.\" Automatically generated by Pod::Man 4.14 (Pod::Simple 3.43) .\" .\" Standard preamble: .\" ======================================================================== .de Sp \" Vertical space (when we can't use .PP) .if t .sp .5v .if n .sp .. .de Vb \" Begin verbatim text .ft CW .nf .ne \\$1 .. .de Ve \" End verbatim text .ft R .fi .. .\" Set up some character translations and predefined strings. \*(-- will .\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left .\" double quote, and \*(R" will give a right double quote. \*(C+ will .\" give a nicer C++. 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Of course, you'll have to process the .\" output yourself in some meaningful fashion. .\" .\" Avoid warning from groff about undefined register 'F'. .de IX .. .nr rF 0 .if \n(.g .if rF .nr rF 1 .if (\n(rF:(\n(.g==0)) \{\ . if \nF \{\ . de IX . tm Index:\\$1\t\\n%\t"\\$2" .. . if !\nF==2 \{\ . nr % 0 . nr F 2 . \} . \} .\} .rr rF .\" ======================================================================== .\" .IX Title "Moose::Cookbook::Meta::Table_MetaclassTrait 3pm" .TH Moose::Cookbook::Meta::Table_MetaclassTrait 3pm "2023-01-30" "perl v5.36.0" "User Contributed Perl Documentation" .\" For nroff, turn off justification. Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "NAME" Moose::Cookbook::Meta::Table_MetaclassTrait \- Adding a "table" attribute as a metaclass trait .SH "VERSION" .IX Header "VERSION" version 2.2203 .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 4 \& # in lib/MyApp/Meta/Class/Trait/HasTable.pm \& package MyApp::Meta::Class::Trait::HasTable; \& use Moose::Role; \& Moose::Util::meta_class_alias(\*(AqHasTable\*(Aq); \& \& has table => ( \& is => \*(Aqrw\*(Aq, \& isa => \*(AqStr\*(Aq, \& ); \& \& # in lib/MyApp/User.pm \& package MyApp::User; \& use Moose \-traits => \*(AqHasTable\*(Aq; \& \& _\|_PACKAGE_\|_\->meta\->table(\*(AqUser\*(Aq); .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" In this recipe, we'll create a class metaclass trait which has a \*(L"table\*(R" attribute. This trait is for classes associated with a \s-1DBMS\s0 table, as one might do for an \s-1ORM.\s0 .PP In this example, the table name is just a string, but in a real \s-1ORM\s0 the table might be an object describing the table. .SH "THE METACLASS TRAIT" .IX Header "THE METACLASS TRAIT" This really is as simple as the recipe \*(L"\s-1SYNOPSIS\*(R"\s0 shows. The trick is getting your classes to use this metaclass, and providing some sort of sugar for declaring the table. This is covered in Moose::Cookbook::Extending::Debugging_BaseClassRole, which shows how to make a module like \f(CW\*(C`Moose.pm\*(C'\fR itself, with sugar like \f(CW\*(C`has_table()\*(C'\fR. .SS "Using this Metaclass Trait in Practice" .IX Subsection "Using this Metaclass Trait in Practice" Accessing this new \f(CW\*(C`table\*(C'\fR attribute is quite simple. Given a class named \f(CW\*(C`MyApp::User\*(C'\fR, we could simply write the following: .PP .Vb 1 \& my $table = MyApp::User\->meta\->table; .Ve .PP As long as \f(CW\*(C`MyApp::User\*(C'\fR has arranged to apply the \&\f(CW\*(C`MyApp::Meta::Class::Trait::HasTable\*(C'\fR to its metaclass, this method call just works. If we want to be more careful, we can check that the class metaclass object has a \f(CW\*(C`table\*(C'\fR method: .PP .Vb 2 \& $table = MyApp::User\->meta\->table \& if MyApp::User\->meta\->can(\*(Aqtable\*(Aq); .Ve .PP In theory, this is not entirely correct, since the metaclass might be getting its \f(CW\*(C`table\*(C'\fR method from a \fIdifferent\fR trait. In practice, you are unlikely to encounter this sort of problem. .SH "RECIPE CAVEAT" .IX Header "RECIPE CAVEAT" This recipe doesn't work when you paste it all into a single file. This is because the \f(CW\*(C`use Moose \-traits => \*(AqHasTable\*(Aq;\*(C'\fR line ends up being executed before the \f(CW\*(C`table\*(C'\fR attribute is defined. .PP When the two packages are separate files, this just works. .SH "SEE ALSO" .IX Header "SEE ALSO" Moose::Cookbook::Meta::Labeled_AttributeTrait \- Labels implemented via attribute traits =pod .SH "AUTHORS" .IX Header "AUTHORS" .IP "\(bu" 4 Stevan Little .IP "\(bu" 4 Dave Rolsky .IP "\(bu" 4 Jesse Luehrs .IP "\(bu" 4 Shawn M Moore .IP "\(bu" 4 יובל קוג'מן (Yuval Kogman) .IP "\(bu" 4 Karen Etheridge .IP "\(bu" 4 Florian Ragwitz .IP "\(bu" 4 Hans Dieter Pearcey .IP "\(bu" 4 Chris Prather .IP "\(bu" 4 Matt S Trout .SH "COPYRIGHT AND LICENSE" .IX Header "COPYRIGHT AND LICENSE" This software is copyright (c) 2006 by Infinity Interactive, Inc. .PP This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.