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package Frost; |
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use strict; |
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use warnings; |
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# LIBS |
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use Moose (); |
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use Moose::Exporter; |
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use Frost::Types; |
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use Frost::Util (); |
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use Frost::Meta::Class; |
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use Frost::Meta::Instance; |
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use Frost::Meta::Constructor; |
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use Frost::Locum; |
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# CLASS VARS |
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# |
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our $VERSION = '0.69_03'; |
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$VERSION = eval $VERSION; |
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our $AUTHORITY = 'cpan:ERNESTO'; |
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# CLASS INIT |
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# |
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Moose::Exporter->setup_import_methods ( also => 'Moose' ); |
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# CLASS METHODS |
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# |
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#sub init_meta |
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#{ |
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# shift; # just your package name |
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# my %options = @_; |
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# |
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# my $meta = Moose->init_meta |
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# ( |
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# %options, |
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# base_class => 'Frost::Locum', |
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# ); |
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# |
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# Moose::Util::MetaRole::apply_metaclass_roles |
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# ( |
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# for_class => $options{for_class}, |
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# metaclass_roles => [ 'Frost::Meta::Class' ], |
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# attribute_metaclass_roles => [ 'Frost::Meta::Attribute' ], |
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# instance_metaclass_roles => [ 'Frost::Meta::Instance' ], |
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# constructor_class_roles => [ 'Frost::Meta::Constructor' ], |
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# ); |
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# |
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# return $meta; |
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#} |
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57
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sub init_meta |
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{ |
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shift; # just your package name |
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my %options = @_; |
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62
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my $meta = Moose->init_meta |
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( |
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%options, |
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base_class => 'Frost::Locum', |
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); |
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68
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Moose::Util::MetaRole::apply_metaroles |
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( |
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for => $options{for_class}, |
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class_metaroles => |
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{ |
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class => [ 'Frost::Meta::Class' ], |
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attribute => [ 'Frost::Meta::Attribute' ], |
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# method |
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# wrapped_method |
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instance => [ 'Frost::Meta::Instance' ], |
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constructor => [ 'Frost::Meta::Constructor' ], |
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# destructor |
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# error |
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} |
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); |
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84
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return $options{for_class}->meta(); |
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} |
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87
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# PUBLIC ATTRIBUTES |
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# |
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90
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# PRIVATE ATTRIBUTES |
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# |
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93
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# CONSTRUCTORS |
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# |
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# DESTRUCTORS |
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# |
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99
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# PUBLIC METHODS |
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# |
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102
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# PRIVATE METHODS |
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# |
104
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105
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# CALLBACKS |
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# |
107
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108
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# IMMUTABLE |
109
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# |
110
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111
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1; |
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113
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__END__ |
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115
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=head1 NAME |
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117
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Frost - Feasible Referential Object STorage |
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119
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=head1 SYNOPSIS |
120
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121
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package My::BaseFoo; |
122
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# use Moose; |
123
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use Frost; |
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125
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has my_base_attr => ( ... ); |
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127
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no Frost; |
128
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__PACKAGE__->meta->make_immutable(); # mutable is VERBOTEN |
129
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130
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################### |
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132
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package My::Foo; |
133
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use Moose; |
134
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extends 'My::BaseFoo'; |
135
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136
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use Frost::Util; # provides true() and false() aka 1 and 0 |
137
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138
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has my_attr => ( ... ); |
139
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has my_index_attr => ( index => true, ... ); |
140
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has my_unique_attr => ( index => 'unique', ... ); |
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has my_transient_attr => ( transient => true, ... ); |
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has my_virtual_attr => ( virtual => true, ... ); |
143
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has my_derived_attr => ( derived => true, ... ); |
144
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145
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sub _build_my_derived_attr { ... } |
146
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147
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no Moose; |
148
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__PACKAGE__->meta->make_immutable(); # mutable is VERBOTEN |
149
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150
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################### |
151
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152
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package My::Bar::AutoId; |
153
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use Moose; |
154
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extends 'My::Foo'; |
155
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156
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use Frost::Util; # provides true() and false() aka 1 and 0 |
157
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158
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has id => ( auto_id => true ); # UUID |
159
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160
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no Moose; |
161
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__PACKAGE__->meta->make_immutable(); |
162
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163
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################### |
164
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165
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package My::Bar::AutoInc; |
166
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use Moose; |
167
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extends 'My::Foo'; |
168
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169
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use Frost::Util; # provides true() and false() aka 1 and 0 |
170
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171
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has id => ( auto_inc => true ); # 1, 2, 3, 4, .... |
172
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173
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no Moose; |
174
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__PACKAGE__->meta->make_immutable(); |
175
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176
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################### |
177
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178
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package My::Loop; |
179
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use Moose; |
180
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extends 'My::BaseFoo'; |
181
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182
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has next => ( isa => 'My::Loop', ... ) # weak ref is VERBOTEN |
183
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has last => ( isa => 'My::Loop', ... ) # weak ref is VERBOTEN |
184
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185
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no Moose; |
186
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__PACKAGE__->meta->make_immutable(); |
187
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188
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################### |
189
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190
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# application.cgi |
191
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# |
192
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use Frost::Asylum; |
193
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use My::Foo; |
194
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use My::Bar::AutoId; |
195
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use My::Bar::AutoInc; |
196
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197
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my $asylum = Frost::Asylum->new ( data_root => '/existing/path/for/my/data' ); |
198
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199
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my ( $id_auto_id, $id_auto_inc ); |
200
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201
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# Create |
202
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{ |
203
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my $foo = My::Foo->new ( id => 42, asylum => $asylum, my_attr => ... ); |
204
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my $bar_id = My::Bar::AutoId->new ( asylum => $asylum, my_attr => ... ); |
205
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my $bar_inc = My::Bar::AutoInc->new ( asylum => $asylum, my_attr => ... ); |
206
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207
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$id_auto_id = $bar_id->id; # something like ECDAEFD4-9247-11DE-9343-7794CBAD412D |
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$id_auto_inc = $bar_inc->id; # if empty 1, otherwise last used id + 1 |
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} |
210
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211
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# Circular references |
212
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{ |
213
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my $loop1 = My::Loop->new ( id => 'L1', asylum => $asylum ); |
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my $loop2 = My::Loop->new ( id => 'L2', asylum => $asylum, last => $loop1 ); |
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my $loop3 = My::Loop->new ( id => 'L3', asylum => $asylum, last => $loop2 ); |
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217
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$loop1->last ( $loop3 ); |
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219
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$loop1->next ( $loop2 ); |
220
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$loop2->next ( $loop3 ); |
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$loop3->next ( $loop1 ); |
222
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} |
223
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224
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$asylum->close; # and auto-save |
225
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226
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# Evoke |
227
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228
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{ |
229
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my $foo = My::Foo->new ( id => 42, asylum => $asylum ); |
230
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my $bar_id = My::Bar::AutoId->new ( id => $id_auto_id, asylum => $asylum ); |
231
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my $bar_inc = My::Bar::AutoInc->new ( id => $id_auto_inc, asylum => $asylum ); |
232
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233
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my $loop2 = My::Loop->new ( id => 'L2', asylum => $asylum ); |
234
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235
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( $loop2->last->id eq 'L1' ) or die; |
236
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( $loop2->next->id eq 'L3' ) or die; |
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my $loop1 = $loop2->next->next; |
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} |
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=head1 ABSTRACT |
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Frost is an extension of Moose providing persistence even to circular structures. |
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=head1 DESCRIPTION |
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Once upon a time, when there were still real winters with frosty air, |
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an old moose named Elly Elk walked through the snow-white forest and |
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murmured over and over "How can I become persistent?", "I want to live |
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forever!" and more and more of that agonizing stuff. |
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Suddenly she ran into Mona Moose, her old friend. Elly noticed, that |
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Mona was looking younger than ever, fresh and clean, although Mona was |
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as old as Elly. "How comes, that you're looking so fine?" Elly said |
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and Mona replied, that she would share her secret with Elly: "Come on, |
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join me at the Asylum." |
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Said and done. The Asylum was a warm and cozy place and the warden was |
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a friendly man, although - with his peaked hat - he looked more like a |
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wizard. The room was dimly lit. Elly recognized many of her old |
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friends hanging out in the Twilight. |
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"Yes, you can live forever as all the other moose, just sign here with |
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blood." the warden said. |
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Elly Elk shivered but Mona Moose encouraged her: "This is a mere |
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formality." |
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What the warden didn't tell, that he was a Necromancer and that behind |
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the Asylum was a big Cemetery, where his assistants - the Morticians - |
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did their clandestine work. But he knew, that - although he was |
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practicing only white magic - the truth would have frighten his |
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guests. |
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"Trust me - I know what I'm doing!" he said and continued: "Look at |
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Mona and all your friends." |
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So Elly Elk signed the registration form and the Necromancer blessed |
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her with an exclusive mantra and said: "With this mantra you'll be |
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unique in the world. As long as it's a known value, you'll live for |
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ever. But now take a sleep - you're looking tired." |
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The Necromancer conducted Elly to his studio, where she was silenced. |
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And as she passed away, he removed her spirit and put it in the |
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Twilight zone. |
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As he came back, Mona wanted to see Elly again. "That's easy!" |
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answered the Necromancer and with a little hex he evoked Elly and |
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turns her from a spirit to - no, not to the original Elly - but to a |
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confusingly similar Locum. |
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"Welcome back, Elly!" Mona said, "You're looking so good now." And |
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really, Elly was feeling young and strong. Mona, Elly and all their |
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friends had much fun all day. |
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In the evening the warden started to silence everybody - um, every |
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Locum - with the magic words "We've done a full day's work and it's |
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time for bed." |
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When the Asylum was closed, the Necromancer absolved all spirits in |
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the Twilight and tasked the Morticians to extract the essence of every |
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spirit and bury it in the Cemetery while collecting every spirit's |
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mantra in a huge book called Illuminator. |
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The next morning, when the Asylum was opened again. the Morticians |
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were instructed by the Necromancer to grub all essences from the |
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Cemetery. His secret assistents did as told: After consulting the |
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Illuminator, they aspirated every mantra to conjure up the spirit from |
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the essence. Then the Necromancer evoked every spirit and so the |
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lounge filled up with Locums again. |
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So it went day in, day out. Elly and Mona and their friends were |
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persistent now and they all lived happily ever after. |
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315
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=head1 MOTIVATION |
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317
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=head2 Persistent storage even for circular structures like trees or loops is feasible |
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319
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As Matt Sergeant pointed out in his article at |
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L<http://www.perl.com/pub/a/2002/08/07/proxyobject.html> using |
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referential structures is problematic, because it leads often to |
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memory leakage. |
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Weak references for object relations like Tree->parent and |
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Tree->children or Loop->next and Loop->last are no solution, because |
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at time the root object is leaving the scope, all references are lost |
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also. |
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Using a proxy object as described in the article is bad too, |
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because deploying a tree constructed with a weak proxy will fail, if you |
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I<hold onto a sub-tree while letting the root of the tree go out of |
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scope. All of a sudden you'll find your data structure has become |
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untangled, like so much wool from a snagged jumper.> (Matt Sergeant) |
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An AUTOLOAD solution would foil L<Moose>' fast immutable mode. Moreover |
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you always have to be sure, which attribute has to be weak or not - an |
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endless source of bugs. |
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339
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But we need referential structures - imagine a repertoire management |
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system for a theatre: |
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We have productions (plays) bound to events (stage performances), |
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while any event points to a production and furthermore to a location, |
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each connected in turn to many productions. Moreover we have authors, |
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directors, technicians, actors etc. attached to events, locations and |
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productions and so on. |
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348
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Loops, loops, loops... |
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350
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The L<Moose> example in t/020_attributes/028_no_slot_access.t gave us the right direction. |
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352
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But just backending all attributes of a complete object - as in the |
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example - wouldn't provide us with a solution for circular references. |
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So why not deliver always a small proxy object (the |
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L<Locum|Frost::Locum>), which holds no real attributes in memory except |
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'id' (the mantra) and 'asylum' (the storage object |
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L<Asylum|Frost::Asylum>) for speed. Every other attribute is |
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kept in a cache (the L<Twilight|Frost::Twilight>) as a unique |
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hash structure (the spirit), which in turn is tied to a L<Berkeley |
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DB|DB_File> backend (the L<Cemetery|Frost::Cemetery>) managed |
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by the L<Necromancer|Frost::Necromancer> and his assistants, |
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the L<Morticians|Frost::Mortician>. |
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364
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Frost's meta voodoo provides us with a lightweight proxy mechanism |
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without AUTOLOAD tricks: Any other object is not stored in the owner |
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object's attribute as a real reference, but only as a special pointer |
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to the other already cached hash (aka spirit). Every time, the referenced |
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object is accessed, the factory (Asylum) delivers a new proxy object (Locum). |
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This way we'll never create hard circular references, which can't be |
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garbage collected. |
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372
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=head1 IMPLEMENTATION |
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374
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=head2 The underlying magic disclosed |
375
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376
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The program: |
377
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378
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# ===> next |
379
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# ---> last |
380
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# |
381
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# +---------+ +---------+ |
382
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# | |====>| | |
383
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# | |<----| | |
384
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# | Loop(1) | | Loop(2) | |
385
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# | |---->| | |
386
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# | |<====| | |
387
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# +---------+ +---------+ |
388
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389
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{ |
390
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package Loop; |
391
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use Frost; |
392
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use Frost::Util; # provides true() and false() aka 1 and 0 |
393
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394
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has content => ( is => 'rw', isa => 'Str' ); |
395
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396
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has 'last' => |
397
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( |
398
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is => 'rw', |
399
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isa => 'Loop', |
400
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weak_ref => false, # weak refs are VERBOTEN |
401
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); |
402
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403
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has 'next' => |
404
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( |
405
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is => 'rw', |
406
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isa => 'Loop', |
407
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weak_ref => false, # weak refs are VERBOTEN |
408
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); |
409
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410
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sub add_next |
411
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{ |
412
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my ( $self, $next ) = @_; |
413
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414
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$next->last ( $self ); |
415
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$self->next ( $next ); |
416
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} |
417
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418
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no Frost; |
419
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420
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__PACKAGE__->meta->make_immutable(); |
421
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} |
422
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423
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use Frost::Asylum; |
424
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425
|
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|
my $asylum = Frost::Asylum->new ( data_root => '/existing/path/for/my/data' ); |
426
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427
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my $loop1 = Loop->new ( asylum => $asylum, id => 1, content => 'This is Loop 1' ); |
428
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my $loop2 = Loop->new ( asylum => $asylum, id => 2, content => 'This is Loop 2' ); |
429
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430
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$loop1->add_next ( $loop2 ); |
431
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$loop2->add_next ( $loop1 ); |
432
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433
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gives us the structures (memory addresses simplified): |
434
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435
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Loop=HASH(100) ( = $loop1 ) |
436
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{ |
437
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id => 1, |
438
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asylum => Asylum=HASH(666), |
439
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_status => "missing", |
440
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} |
441
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442
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Loop=HASH(200) ( = $loop2 ) |
443
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{ |
444
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id => 2, |
445
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asylum => Asylum=HASH(666), |
446
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_status => "missing", |
447
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} |
448
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449
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Asylum=HASH(666) |
450
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{ |
451
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twilight => Twilight=HASH(42) |
452
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{ |
453
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'Loop|1' => { id => 1, _dirty => false, |
454
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content => 'This is Loop 1', |
455
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next => { type => 'Loop', ref => 2 }, last => { type => 'Loop', ref => 2 } }, |
456
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'Loop|2' => { id => 2, _dirty => true, |
457
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content => 'This is Loop 2', |
458
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next => { type => 'Loop', ref => 1 }, last => { type => 'Loop', ref => 1 } }, |
459
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} |
460
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} |
461
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462
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|
Loop 1 in the Twilight is NOT dirty as one may expect, because it was saved |
463
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automatically during silencing due to the referential structure. |
464
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|
465
|
|
|
|
|
|
|
Somewhere else in the program: |
466
|
|
|
|
|
|
|
|
467
|
|
|
|
|
|
|
{ |
468
|
|
|
|
|
|
|
my $loop1n2 = $loop1->next(); |
469
|
|
|
|
|
|
|
my $loop1l2 = $loop1->last(); |
470
|
|
|
|
|
|
|
|
471
|
|
|
|
|
|
|
my $loop2n1 = $loop2->next(); |
472
|
|
|
|
|
|
|
my $loop2l1 = $loop2->last(); |
473
|
|
|
|
|
|
|
} |
474
|
|
|
|
|
|
|
|
475
|
|
|
|
|
|
|
gives us the structures: |
476
|
|
|
|
|
|
|
|
477
|
|
|
|
|
|
|
Loop=HASH(300) ( = $loop1n2 ) |
478
|
|
|
|
|
|
|
{ |
479
|
|
|
|
|
|
|
id => 2, |
480
|
|
|
|
|
|
|
asylum => Asylum=HASH(666), |
481
|
|
|
|
|
|
|
_status => "exists", |
482
|
|
|
|
|
|
|
} |
483
|
|
|
|
|
|
|
|
484
|
|
|
|
|
|
|
Loop=HASH(400) ( = $loop1l2 ) |
485
|
|
|
|
|
|
|
{ |
486
|
|
|
|
|
|
|
id => 2, |
487
|
|
|
|
|
|
|
asylum => Asylum=HASH(666), |
488
|
|
|
|
|
|
|
_status => "exists", |
489
|
|
|
|
|
|
|
} |
490
|
|
|
|
|
|
|
|
491
|
|
|
|
|
|
|
Loop=HASH(500) ( = $loop2n1 ) |
492
|
|
|
|
|
|
|
{ |
493
|
|
|
|
|
|
|
id => 1, |
494
|
|
|
|
|
|
|
asylum => Asylum=HASH(666), |
495
|
|
|
|
|
|
|
_status => "exists", |
496
|
|
|
|
|
|
|
} |
497
|
|
|
|
|
|
|
|
498
|
|
|
|
|
|
|
Loop=HASH(600) ( = $loop2l1 ) |
499
|
|
|
|
|
|
|
{ |
500
|
|
|
|
|
|
|
id => 1, |
501
|
|
|
|
|
|
|
asylum => Asylum=HASH(666), |
502
|
|
|
|
|
|
|
_status => "exists", |
503
|
|
|
|
|
|
|
} |
504
|
|
|
|
|
|
|
|
505
|
|
|
|
|
|
|
The Twilight has not changed: |
506
|
|
|
|
|
|
|
|
507
|
|
|
|
|
|
|
Asylum=HASH(666) |
508
|
|
|
|
|
|
|
{ |
509
|
|
|
|
|
|
|
twilight => Twilight=HASH(42) |
510
|
|
|
|
|
|
|
{ |
511
|
|
|
|
|
|
|
'Loop|1' => { id => 1, _dirty => false, |
512
|
|
|
|
|
|
|
content => 'This is Loop 1', |
513
|
|
|
|
|
|
|
next => { type => 'Loop', ref => 2 }, last => { type => 'Loop', ref => 2 } }, |
514
|
|
|
|
|
|
|
'Loop|2' => { id => 2, _dirty => true, |
515
|
|
|
|
|
|
|
content => 'This is Loop 2', |
516
|
|
|
|
|
|
|
next => { type => 'Loop', ref => 1 }, last => { type => 'Loop', ref => 1 } }, |
517
|
|
|
|
|
|
|
} |
518
|
|
|
|
|
|
|
} |
519
|
|
|
|
|
|
|
|
520
|
|
|
|
|
|
|
But we got new instances: |
521
|
|
|
|
|
|
|
|
522
|
|
|
|
|
|
|
Loop=HASH(300) != Loop=HASH(200) |
523
|
|
|
|
|
|
|
Loop=HASH(400) != Loop=HASH(200) |
524
|
|
|
|
|
|
|
Loop=HASH(500) != Loop=HASH(100) |
525
|
|
|
|
|
|
|
Loop=HASH(600) != Loop=HASH(100) |
526
|
|
|
|
|
|
|
|
527
|
|
|
|
|
|
|
Continuing the program: |
528
|
|
|
|
|
|
|
|
529
|
|
|
|
|
|
|
my $loop3 = Loop->new ( asylum => $asylum, id => 3, content => 'This is Loop 3' ); |
530
|
|
|
|
|
|
|
|
531
|
|
|
|
|
|
|
$loop1->add_next ( $loop3 ); |
532
|
|
|
|
|
|
|
$loop3->add_next ( $loop2 ); |
533
|
|
|
|
|
|
|
|
534
|
|
|
|
|
|
|
gives us the structures: |
535
|
|
|
|
|
|
|
|
536
|
|
|
|
|
|
|
Loop=HASH(333) ( = $loop3 ) |
537
|
|
|
|
|
|
|
{ |
538
|
|
|
|
|
|
|
id => 3, |
539
|
|
|
|
|
|
|
asylum => Asylum=HASH(666), |
540
|
|
|
|
|
|
|
_status => "missing", |
541
|
|
|
|
|
|
|
} |
542
|
|
|
|
|
|
|
|
543
|
|
|
|
|
|
|
Asylum=HASH(666) |
544
|
|
|
|
|
|
|
{ |
545
|
|
|
|
|
|
|
twilight => Twilight=HASH(42) |
546
|
|
|
|
|
|
|
{ |
547
|
|
|
|
|
|
|
'Loop|1' => { id => 1, _dirty => true, |
548
|
|
|
|
|
|
|
content => 'This is Loop 1', |
549
|
|
|
|
|
|
|
next => { type => 'Loop', ref => 3 }, last => { type => 'Loop', ref => 2 } }, |
550
|
|
|
|
|
|
|
'Loop|2' => { id => 2, _dirty => false, |
551
|
|
|
|
|
|
|
content => 'This is Loop 2', |
552
|
|
|
|
|
|
|
next => { type => 'Loop', ref => 1 }, last => { type => 'Loop', ref => 3 } }, |
553
|
|
|
|
|
|
|
'Loop|3' => { id => 3, _dirty => true, |
554
|
|
|
|
|
|
|
content => 'This is Loop 3', |
555
|
|
|
|
|
|
|
next => { type => 'Loop', ref => 2 }, last => { type => 'Loop', ref => 1 } }, |
556
|
|
|
|
|
|
|
} |
557
|
|
|
|
|
|
|
} |
558
|
|
|
|
|
|
|
|
559
|
|
|
|
|
|
|
Now Loop 2 in the Twilight is NOT dirty, but the others. Which Locum |
560
|
|
|
|
|
|
|
was automatically saved depends on the order of entering the |
561
|
|
|
|
|
|
|
referential structure - adding to $loop3 first i.e.: |
562
|
|
|
|
|
|
|
|
563
|
|
|
|
|
|
|
$loop3->add_next ( $loop2 ); |
564
|
|
|
|
|
|
|
$loop1->add_next ( $loop3 ); |
565
|
|
|
|
|
|
|
|
566
|
|
|
|
|
|
|
would yield: |
567
|
|
|
|
|
|
|
|
568
|
|
|
|
|
|
|
Asylum=HASH(666) |
569
|
|
|
|
|
|
|
{ |
570
|
|
|
|
|
|
|
twilight => Twilight=HASH(42) |
571
|
|
|
|
|
|
|
{ |
572
|
|
|
|
|
|
|
'Loop|1' => { id => 1, _dirty => true, |
573
|
|
|
|
|
|
|
content => 'This is Loop 1', |
574
|
|
|
|
|
|
|
next => { type => 'Loop', ref => 3 }, last => { type => 'Loop', ref => 2 } }, |
575
|
|
|
|
|
|
|
'Loop|2' => { id => 2, _dirty => false, |
576
|
|
|
|
|
|
|
content => 'This is Loop 2', |
577
|
|
|
|
|
|
|
next => { type => 'Loop', ref => 1 }, last => { type => 'Loop', ref => 3 } }, |
578
|
|
|
|
|
|
|
'Loop|3' => { id => 3, _dirty => false, |
579
|
|
|
|
|
|
|
content => 'This is Loop 3', |
580
|
|
|
|
|
|
|
next => { type => 'Loop', ref => 2 }, last => { type => 'Loop', ref => 1 } }, |
581
|
|
|
|
|
|
|
} |
582
|
|
|
|
|
|
|
} |
583
|
|
|
|
|
|
|
|
584
|
|
|
|
|
|
|
But this doesn't matter, as long as you always close the Asylum. This |
585
|
|
|
|
|
|
|
will auto-save all remaining dirty Loops: |
586
|
|
|
|
|
|
|
|
587
|
|
|
|
|
|
|
$asylum->close(); |
588
|
|
|
|
|
|
|
|
589
|
|
|
|
|
|
|
What the user wanted: |
590
|
|
|
|
|
|
|
|
591
|
|
|
|
|
|
|
# ===> next |
592
|
|
|
|
|
|
|
# ---> last |
593
|
|
|
|
|
|
|
# |
594
|
|
|
|
|
|
|
# +---------+ +---------+ +---------+ |
595
|
|
|
|
|
|
|
# | |====>| |====>| | |
596
|
|
|
|
|
|
|
# | |<----| |<----| | |
597
|
|
|
|
|
|
|
# | Loop(1) | | Loop(3) | | Loop(2) | |
598
|
|
|
|
|
|
|
# | | | | | | |
599
|
|
|
|
|
|
|
# | | | | | | |
600
|
|
|
|
|
|
|
# | | | | | | |
601
|
|
|
|
|
|
|
# | | | | | | |
602
|
|
|
|
|
|
|
# | | +---------+ | | |
603
|
|
|
|
|
|
|
# | |-------------------->| | |
604
|
|
|
|
|
|
|
# | |<====================| | |
605
|
|
|
|
|
|
|
# +---------+ +---------+ |
606
|
|
|
|
|
|
|
|
607
|
|
|
|
|
|
|
could easily be reloaded - in another script the next day just say: |
608
|
|
|
|
|
|
|
|
609
|
|
|
|
|
|
|
my $loop3 = Loop->new ( id => 3, asylum => $asylum ); |
610
|
|
|
|
|
|
|
|
611
|
|
|
|
|
|
|
print $loop3->content; # 'This is Loop 3' |
612
|
|
|
|
|
|
|
|
613
|
|
|
|
|
|
|
print $loop3->last->content; # 'This is Loop 1' |
614
|
|
|
|
|
|
|
print $loop3->next->content; # 'This is Loop 2' |
615
|
|
|
|
|
|
|
print $loop3->next->next->content; # 'This is Loop 1' |
616
|
|
|
|
|
|
|
print $loop3->last->next->content; # 'This is Loop 3' |
617
|
|
|
|
|
|
|
|
618
|
|
|
|
|
|
|
|
619
|
|
|
|
|
|
|
=head2 My friend Jack eats sugar lumps - more fun with attributes |
620
|
|
|
|
|
|
|
|
621
|
|
|
|
|
|
|
Frost comes with six new features extending L<Moose::Meta::Attribute>. |
622
|
|
|
|
|
|
|
|
623
|
|
|
|
|
|
|
They provide some sugar to deal with the location of an attribute, |
624
|
|
|
|
|
|
|
to save some typing and to create indices. |
625
|
|
|
|
|
|
|
|
626
|
|
|
|
|
|
|
So migrating from a SQL database to an object-oriented storage is |
627
|
|
|
|
|
|
|
possible without loosing one of the main features of a relational |
628
|
|
|
|
|
|
|
database: indexing. |
629
|
|
|
|
|
|
|
|
630
|
|
|
|
|
|
|
=over 4 |
631
|
|
|
|
|
|
|
|
632
|
|
|
|
|
|
|
=item transient |
633
|
|
|
|
|
|
|
|
634
|
|
|
|
|
|
|
has foo => ( transient => true, ... ); |
635
|
|
|
|
|
|
|
|
636
|
|
|
|
|
|
|
A C<transient> attribute lives at run-time and is B<"local"> : |
637
|
|
|
|
|
|
|
|
638
|
|
|
|
|
|
|
It B<becomes undef>, when the Locum object goes B<out of scope>, and it's B<not saved>. |
639
|
|
|
|
|
|
|
|
640
|
|
|
|
|
|
|
=item virtual |
641
|
|
|
|
|
|
|
|
642
|
|
|
|
|
|
|
has bar => ( virtual => true, ... ); |
643
|
|
|
|
|
|
|
|
644
|
|
|
|
|
|
|
A C<virtual> attribute lives at run-time and is B<"global"> : |
645
|
|
|
|
|
|
|
|
646
|
|
|
|
|
|
|
It's B<still present>, when the Locum object goes B<out of scope>, but it's B<not saved>. |
647
|
|
|
|
|
|
|
|
648
|
|
|
|
|
|
|
=item derived |
649
|
|
|
|
|
|
|
|
650
|
|
|
|
|
|
|
has dat => ( derived => true, ... ); |
651
|
|
|
|
|
|
|
|
652
|
|
|
|
|
|
|
A C<derived> attribute lives at run-time and is B<"global"> : |
653
|
|
|
|
|
|
|
|
654
|
|
|
|
|
|
|
It's B<still present>, when the Locum object goes B<out of scope>, but it's B<not saved>. |
655
|
|
|
|
|
|
|
|
656
|
|
|
|
|
|
|
# The definition: |
657
|
|
|
|
|
|
|
|
658
|
|
|
|
|
|
|
has dat => ( derived => true, isa => 'Str' ); |
659
|
|
|
|
|
|
|
|
660
|
|
|
|
|
|
|
# is a shortcut for: |
661
|
|
|
|
|
|
|
|
662
|
|
|
|
|
|
|
has dat => ( virtual => true, isa => 'Str', is => 'ro', init_arg => undef, lazy_build => true ); |
663
|
|
|
|
|
|
|
|
664
|
|
|
|
|
|
|
# which becomes: |
665
|
|
|
|
|
|
|
|
666
|
|
|
|
|
|
|
has dat => |
667
|
|
|
|
|
|
|
( |
668
|
|
|
|
|
|
|
virtual => true, # from derived |
669
|
|
|
|
|
|
|
is => 'ro', # |
670
|
|
|
|
|
|
|
init_arg => undef, # |
671
|
|
|
|
|
|
|
isa => 'Str', |
672
|
|
|
|
|
|
|
lazy => true, # from lazy_build |
673
|
|
|
|
|
|
|
builder => '_build_dat', # |
674
|
|
|
|
|
|
|
clearer => 'clear_dat', # |
675
|
|
|
|
|
|
|
predicate => 'has_dat', # |
676
|
|
|
|
|
|
|
); |
677
|
|
|
|
|
|
|
|
678
|
|
|
|
|
|
|
# and requires: |
679
|
|
|
|
|
|
|
|
680
|
|
|
|
|
|
|
sub _build_dat { ... } |
681
|
|
|
|
|
|
|
|
682
|
|
|
|
|
|
|
=item index |
683
|
|
|
|
|
|
|
|
684
|
|
|
|
|
|
|
package Foo; |
685
|
|
|
|
|
|
|
... |
686
|
|
|
|
|
|
|
has foo => ( index => true, ... ); |
687
|
|
|
|
|
|
|
has bar => ( index => 'unique', ... ); |
688
|
|
|
|
|
|
|
|
689
|
|
|
|
|
|
|
This creates a multiple or unique index |
690
|
|
|
|
|
|
|
(L<Frost::Illuminator>) of the attribute values. Numeric sorting is automatically |
691
|
|
|
|
|
|
|
determined from the attribute's C<isa>. |
692
|
|
|
|
|
|
|
|
693
|
|
|
|
|
|
|
Thus, if you create objects with following attributes: |
694
|
|
|
|
|
|
|
|
695
|
|
|
|
|
|
|
{ id => 'id1', foo => 'foo1', bar => 'bar1' } |
696
|
|
|
|
|
|
|
{ id => 'id2', foo => 'foo2', bar => 'bar2' } |
697
|
|
|
|
|
|
|
{ id => 'id3', foo => 'foo3', bar => 'bar3' } |
698
|
|
|
|
|
|
|
{ id => 'id4', foo => 'foo3', bar => 'bar2' } |
699
|
|
|
|
|
|
|
{ id => 'id5', foo => 'foo1', bar => 'bar3' } |
700
|
|
|
|
|
|
|
|
701
|
|
|
|
|
|
|
you'll get two indices: |
702
|
|
|
|
|
|
|
|
703
|
|
|
|
|
|
|
foo1 -> id1 |
704
|
|
|
|
|
|
|
foo1 -> id5 |
705
|
|
|
|
|
|
|
foo2 -> id2 |
706
|
|
|
|
|
|
|
foo3 -> id3 |
707
|
|
|
|
|
|
|
foo3 -> id4 |
708
|
|
|
|
|
|
|
|
709
|
|
|
|
|
|
|
bar1 -> id1 |
710
|
|
|
|
|
|
|
id2 silently eaten... |
711
|
|
|
|
|
|
|
id3 silently eaten... |
712
|
|
|
|
|
|
|
bar2 -> id4 |
713
|
|
|
|
|
|
|
bar3 -> id5 |
714
|
|
|
|
|
|
|
|
715
|
|
|
|
|
|
|
Later you can search in the unique index: |
716
|
|
|
|
|
|
|
|
717
|
|
|
|
|
|
|
my $id = $asylum->find ( 'Foo', 'bar3', 'bar' ); # class, key, attribute_name |
718
|
|
|
|
|
|
|
|
719
|
|
|
|
|
|
|
# $id is 'id5' |
720
|
|
|
|
|
|
|
|
721
|
|
|
|
|
|
|
my $foo = Foo->new ( id => $id, asylum => $asylum ); |
722
|
|
|
|
|
|
|
|
723
|
|
|
|
|
|
|
or iterate over the multiple index: |
724
|
|
|
|
|
|
|
|
725
|
|
|
|
|
|
|
my $id = $asylum->first ( 'Foo', 'foo1', 'foo' ); # class, key, attribute_name |
726
|
|
|
|
|
|
|
|
727
|
|
|
|
|
|
|
while ( $id ) |
728
|
|
|
|
|
|
|
# 1st loop: $id is 'id1' |
729
|
|
|
|
|
|
|
# 2nd loop: $id is 'id5' |
730
|
|
|
|
|
|
|
# 3rd loop: $id is '' |
731
|
|
|
|
|
|
|
{ |
732
|
|
|
|
|
|
|
my $foo = Foo->new ( id => $id, asylum => $asylum ); |
733
|
|
|
|
|
|
|
|
734
|
|
|
|
|
|
|
$id = $asylum->next ( 'Foo', 'foo1', 'foo' ); |
735
|
|
|
|
|
|
|
} |
736
|
|
|
|
|
|
|
|
737
|
|
|
|
|
|
|
and much more - see L<Frost::Asylum>. |
738
|
|
|
|
|
|
|
|
739
|
|
|
|
|
|
|
=item auto_id |
740
|
|
|
|
|
|
|
|
741
|
|
|
|
|
|
|
has id => ( auto_id => true, ... ); |
742
|
|
|
|
|
|
|
has +id => ( auto_id => true, ... ); |
743
|
|
|
|
|
|
|
|
744
|
|
|
|
|
|
|
If the basic attribute B<id> is sweetened with C<auto_id>, the instance |
745
|
|
|
|
|
|
|
is automatically assigned a UUID - see L<Data::UUID>. |
746
|
|
|
|
|
|
|
|
747
|
|
|
|
|
|
|
The resulting B<id> is something like C<ECDAEFD4-9247-11DE-9343-7794CBAD412D>. |
748
|
|
|
|
|
|
|
|
749
|
|
|
|
|
|
|
=item auto_inc |
750
|
|
|
|
|
|
|
|
751
|
|
|
|
|
|
|
has id => ( auto_inc => true, ... ); |
752
|
|
|
|
|
|
|
has +id => ( auto_inc => true, ... ); |
753
|
|
|
|
|
|
|
|
754
|
|
|
|
|
|
|
If the basic attribute B<id> is sweetened with C<auto_inc>, the |
755
|
|
|
|
|
|
|
instance is automatically assigned a sequential number: I<highest used |
756
|
|
|
|
|
|
|
id> + 1, where I<highest used id> = 0 in an empty cemetery. |
757
|
|
|
|
|
|
|
|
758
|
|
|
|
|
|
|
=back |
759
|
|
|
|
|
|
|
|
760
|
|
|
|
|
|
|
See L<Frost::Meta::Attribute> |
761
|
|
|
|
|
|
|
|
762
|
|
|
|
|
|
|
=head1 The Four Commandments of Frost |
763
|
|
|
|
|
|
|
|
764
|
|
|
|
|
|
|
=head2 Thou shalt absolve no other Moose before Locum |
765
|
|
|
|
|
|
|
|
766
|
|
|
|
|
|
|
Frost can only store L<Moose> objects, more precisely: objects inheriting |
767
|
|
|
|
|
|
|
from L<Frost::Locum>. |
768
|
|
|
|
|
|
|
|
769
|
|
|
|
|
|
|
This does not mean, that each of your old classes must now use |
770
|
|
|
|
|
|
|
Frost instead of L<Moose>. Migrating is easily possible by |
771
|
|
|
|
|
|
|
creating or changing a base class from C<use Moose> to C<use |
772
|
|
|
|
|
|
|
Frost> - i.e. |
773
|
|
|
|
|
|
|
|
774
|
|
|
|
|
|
|
package My::BaseFoo; |
775
|
|
|
|
|
|
|
# use Moose; |
776
|
|
|
|
|
|
|
use Frost; |
777
|
|
|
|
|
|
|
|
778
|
|
|
|
|
|
|
no Frost; |
779
|
|
|
|
|
|
|
__PACKAGE__->meta->make_immutable(); # mutable is VERBOTEN |
780
|
|
|
|
|
|
|
|
781
|
|
|
|
|
|
|
package My::Foo; |
782
|
|
|
|
|
|
|
use Moose; |
783
|
|
|
|
|
|
|
extends 'My::BaseFoo'; |
784
|
|
|
|
|
|
|
|
785
|
|
|
|
|
|
|
has my_attr => ( ... ); |
786
|
|
|
|
|
|
|
|
787
|
|
|
|
|
|
|
no Moose; |
788
|
|
|
|
|
|
|
__PACKAGE__->meta->make_immutable(); # mutable is VERBOTEN |
789
|
|
|
|
|
|
|
|
790
|
|
|
|
|
|
|
Thus My::Foo and all inheriting classes can be defined the usual L<Moose> |
791
|
|
|
|
|
|
|
way. The class My::BaseFoo inherits from Frost::Locum, pulling |
792
|
|
|
|
|
|
|
in all its persistence stuff. |
793
|
|
|
|
|
|
|
|
794
|
|
|
|
|
|
|
=head2 Thou shalt honor immutability |
795
|
|
|
|
|
|
|
|
796
|
|
|
|
|
|
|
While applying L<Moose>' tests for Frost it appeared, that reblessing an |
797
|
|
|
|
|
|
|
object - i.e. because of applying a role at run-time - creates mutable |
798
|
|
|
|
|
|
|
objects blessed in an anonymous class. This destroys the silence/evoke |
799
|
|
|
|
|
|
|
mechanism, which depends on the real classname. |
800
|
|
|
|
|
|
|
|
801
|
|
|
|
|
|
|
So reblessing as well as make_mutable is VERBOTEN. |
802
|
|
|
|
|
|
|
|
803
|
|
|
|
|
|
|
=head2 Thou shalt not weaken thy reference |
804
|
|
|
|
|
|
|
|
805
|
|
|
|
|
|
|
Due to Frost's proxy algorithm there is no need for weak references. |
806
|
|
|
|
|
|
|
See L</MOTIVATION>. |
807
|
|
|
|
|
|
|
|
808
|
|
|
|
|
|
|
=head2 Thou shalt not create or load objects without an id and thy asylum |
809
|
|
|
|
|
|
|
|
810
|
|
|
|
|
|
|
To create a new frostable object you must always say: |
811
|
|
|
|
|
|
|
|
812
|
|
|
|
|
|
|
my $foo = Foo->new ( id => 'a_unique_id', asylum => $asylum, an_attr => ..., another_attr => ... ); |
813
|
|
|
|
|
|
|
|
814
|
|
|
|
|
|
|
$remembered_id = $foo->id; |
815
|
|
|
|
|
|
|
|
816
|
|
|
|
|
|
|
And to reload a frosted object just say: |
817
|
|
|
|
|
|
|
|
818
|
|
|
|
|
|
|
my $foo = Foo->new ( id => $remembered_id, asylum => $asylum ); # other params ignored |
819
|
|
|
|
|
|
|
|
820
|
|
|
|
|
|
|
Or use the Asylum API - a matter of taste: |
821
|
|
|
|
|
|
|
|
822
|
|
|
|
|
|
|
my $remembered_id = 'a_unique_id'; |
823
|
|
|
|
|
|
|
|
824
|
|
|
|
|
|
|
my $foo = $asylum->silence ( 'Foo', $remembered_id, an_attr => ..., another_attr => ... ); |
825
|
|
|
|
|
|
|
|
826
|
|
|
|
|
|
|
# later... |
827
|
|
|
|
|
|
|
|
828
|
|
|
|
|
|
|
my $foo = $asylum->evoke ( 'Foo', $remembered_id ); # other params ignored |
829
|
|
|
|
|
|
|
|
830
|
|
|
|
|
|
|
If the C<id> is defined with C<auto_id> or C<auto_inc>, Asylum is creating a mantra for you - i.e.: |
831
|
|
|
|
|
|
|
|
832
|
|
|
|
|
|
|
package Bar; |
833
|
|
|
|
|
|
|
... |
834
|
|
|
|
|
|
|
has id ( auto_id => 1 ); |
835
|
|
|
|
|
|
|
... |
836
|
|
|
|
|
|
|
|
837
|
|
|
|
|
|
|
# Create and silence without id: |
838
|
|
|
|
|
|
|
# |
839
|
|
|
|
|
|
|
my $bar = Bar->new ( asylum => $asylum, an_attr => ..., another_attr => ... ); |
840
|
|
|
|
|
|
|
|
841
|
|
|
|
|
|
|
my $bar_id = $bar->id; # something like ECDAEFD4-9247-11DE-9343-7794CBAD412D |
842
|
|
|
|
|
|
|
|
843
|
|
|
|
|
|
|
# Evoke with id: |
844
|
|
|
|
|
|
|
# |
845
|
|
|
|
|
|
|
my $bar = Bar->new ( id => $bar_id, asylum => $asylum ); |
846
|
|
|
|
|
|
|
|
847
|
|
|
|
|
|
|
=head1 TODO |
848
|
|
|
|
|
|
|
|
849
|
|
|
|
|
|
|
Docs, docs, docs... |
850
|
|
|
|
|
|
|
|
851
|
|
|
|
|
|
|
=head1 GETTING HELP |
852
|
|
|
|
|
|
|
|
853
|
|
|
|
|
|
|
I'm reading the L<Moose> mailing list frequently, so please ask your |
854
|
|
|
|
|
|
|
questions there. |
855
|
|
|
|
|
|
|
|
856
|
|
|
|
|
|
|
The mailing list is L<moose@perl.org>. You must be subscribed to send |
857
|
|
|
|
|
|
|
a message. To subscribe, send an empty message to |
858
|
|
|
|
|
|
|
L<moose-subscribe@perl.org> |
859
|
|
|
|
|
|
|
|
860
|
|
|
|
|
|
|
=head1 DEPENDENCIES |
861
|
|
|
|
|
|
|
|
862
|
|
|
|
|
|
|
This module requires these other modules and libraries: |
863
|
|
|
|
|
|
|
|
864
|
|
|
|
|
|
|
Carp |
865
|
|
|
|
|
|
|
Class::MOP |
866
|
|
|
|
|
|
|
Data::Dumper |
867
|
|
|
|
|
|
|
Data::UUID |
868
|
|
|
|
|
|
|
DB_File |
869
|
|
|
|
|
|
|
Exporter |
870
|
|
|
|
|
|
|
Fcntl |
871
|
|
|
|
|
|
|
File::Path |
872
|
|
|
|
|
|
|
IO::File |
873
|
|
|
|
|
|
|
Log::Log4perl |
874
|
|
|
|
|
|
|
Moose |
875
|
|
|
|
|
|
|
Scalar::Util |
876
|
|
|
|
|
|
|
Storable |
877
|
|
|
|
|
|
|
Tie::Cache::LRU |
878
|
|
|
|
|
|
|
Time::HiRes |
879
|
|
|
|
|
|
|
|
880
|
|
|
|
|
|
|
For testing these modules are needed: |
881
|
|
|
|
|
|
|
|
882
|
|
|
|
|
|
|
DateTime::Format::MySQL |
883
|
|
|
|
|
|
|
List::Util |
884
|
|
|
|
|
|
|
List::MoreUtils |
885
|
|
|
|
|
|
|
Test::Deep |
886
|
|
|
|
|
|
|
Test::Differences |
887
|
|
|
|
|
|
|
Test::Exception |
888
|
|
|
|
|
|
|
Test::More |
889
|
|
|
|
|
|
|
|
890
|
|
|
|
|
|
|
Optional modules to run some tests: |
891
|
|
|
|
|
|
|
|
892
|
|
|
|
|
|
|
Devel::Size |
893
|
|
|
|
|
|
|
Sys::MemInfo |
894
|
|
|
|
|
|
|
Declare::Constraints::Simple |
895
|
|
|
|
|
|
|
Regexp::Common |
896
|
|
|
|
|
|
|
Locale::US |
897
|
|
|
|
|
|
|
|
898
|
|
|
|
|
|
|
Please see Makefile.PL for required versions. |
899
|
|
|
|
|
|
|
|
900
|
|
|
|
|
|
|
=head1 BUGS |
901
|
|
|
|
|
|
|
|
902
|
|
|
|
|
|
|
All complex software has bugs lurking in it, and this module is no |
903
|
|
|
|
|
|
|
exception. |
904
|
|
|
|
|
|
|
|
905
|
|
|
|
|
|
|
Please report any bugs to me or the mailing list. |
906
|
|
|
|
|
|
|
|
907
|
|
|
|
|
|
|
=head1 AUTHOR |
908
|
|
|
|
|
|
|
|
909
|
|
|
|
|
|
|
Ernesto L<ernesto@dienstleistung-kultur.de> |
910
|
|
|
|
|
|
|
|
911
|
|
|
|
|
|
|
=head1 COPYRIGHT AND LICENSE |
912
|
|
|
|
|
|
|
|
913
|
|
|
|
|
|
|
Copyright (C) 2010 by Dienstleistung Kultur Ltd. & Co. KG |
914
|
|
|
|
|
|
|
|
915
|
|
|
|
|
|
|
L<http://dienstleistung-kultur.de/frost/> |
916
|
|
|
|
|
|
|
|
917
|
|
|
|
|
|
|
This library is free software; you can redistribute it and/or modify |
918
|
|
|
|
|
|
|
it under the same terms as Perl itself. |
919
|
|
|
|
|
|
|
|
920
|
|
|
|
|
|
|
=cut |
921
|
|
|
|
|
|
|
|
922
|
|
|
|
|
|
|
|