Method::Lexical - private methods and lexical method overrides
package MyPragma; use base qw(Method::Lexical); sub import { shift->SUPER::import( 'private' => sub { ... }, 'UNIVERSAL::dump' => '+Data::Dump::pp' ) }
#!/usr/bin/env perl my $self = bless {}; { use MyPragma; $self->private(); # OK $self->dump(); # OK } $self->private; # Can't locate object method "private" via package "main" $self->dump; # Can't locate object method "dump" via package "main"
Method::Lexical is a lexically-scoped pragma that implements lexical methods i.e. methods whose use is restricted to the lexical scope in which they are imported or declared.
Method::Lexical
The use Method::Lexical statement takes a hashref or a list of key/value pairs in which the keys are method names and the values are subroutine references or strings containing the package-qualified name of the method to be called. Unqualifed method names in keys are installed as methods in the currently-compiling package. The following example summarizes the types of keys and values that can be supplied.
use Method::Lexical
use Method::Lexical { foo => \&foo, # unqualified method-name key: installed in the currently-compiling package e.g. main::foo MyClass::foo => \&foo, # qualified method-name key: installed in the specified package bar => sub { ... }, # anonymous sub value baz => \&baz, # coderef value quux => 'main::quux', # sub name value: unqualified names are resolved to the currently-compiling package dump => '+Data::Dump::dump', # autoload Data::Dump 'UNIVERSAL::dump' => \&Data::Dump::dump, # define a universal method 'UNIVERSAL::isa' => \&my_isa, # override a universal method '-autoload' => 1, # autoload modules for all subs passed by name '-debug' => 1 # show diagnostic messages };
Method::Lexical options are prefixed with a hyphen to distinguish them from method names. The following options are supported.
If the value is a string containing a package-qualified subroutine name, then the subroutine's module is automatically loaded. This can either be done on a per-method basis by prefixing the value with a +, or for all value arguments with qualified names by supplying the -autoload option with a true value e.g.
value
+
-autoload
use Method::Lexical { foo => 'MyFoo::foo', bar => 'MyBar::bar', baz => 'MyBaz::baz', '-autoload' => 1 };
or
use MyFoo; use MyBaz; use Method::Lexical foo => 'MyFoo::foo', bar => '+MyBar::bar', # autoload MyBar baz => 'MyBaz::baz';
This option should not be confused with lexical AUTOLOAD methods, which are also supported e.g.
use Method::Lexical AUTOLOAD => sub { ... }, 'UNIVERSAL::AUTOLOAD' => \&autoload;
A trace of the module's actions can be enabled or disabled lexically by supplying the -debug option with a true or false value. The trace is printed to STDERR.
-debug
e.g.
use Method::Lexical { foo => \&foo, bar => sub { ... }, '-debug' => 1 };
Method::Lexical::import can be called indirectly via use Method::Lexical or can be overridden by subclasses to create lexically-scoped pragmas that export methods whose use is restricted to the calling scope e.g.
Method::Lexical::import
package Universal::Dump; use base qw(Method::Lexical); sub import { shift->SUPER::import('UNIVERSAL::dump' => '+Data::Dump::dump') } 1;
Client code can then import lexical methods from the module:
#!/usr/bin/env perl use CGI; { use Universal::Dump; say CGI->new->dump; # OK } eval { CGI->new->dump }; warn $@; # Can't locate object method "dump" via package "CGI"
Method::Lexical::unimport removes the specified lexical methods from the current scope, or all lexical methods if no arguments are supplied.
Method::Lexical::unimport
use Method::Lexical foo => \&foo; my $self = bless {}; { use Method::Lexical bar => sub { ... }, 'UNIVERSAL::baz' => sub { ... }; $self->foo(); # OK $self->bar(); # OK $self->baz(); # OK no Method::Lexical qw(foo); eval { $self->foo() }; warn $@; # Can't locate object method "foo" via package "main" $self->bar(); # OK $self->baz(); # OK no Method::Lexical; eval { $self->bar() }; warn $@; # Can't locate object method "bar" via package "main" eval { $self->baz() }; warn $@; # Can't locate object method "baz" via package "main" } $self->foo(); # OK
Unimports are specific to the class supplied in the no statement, so pragmas that subclass Method::Lexical inherit an unimport method that only removes the methods they installed e.g.
no
unimport
{ use MyPragma qw(foo bar baz); use Method::Lexical quux => \&quux; $self->foo(); # OK $self->quux(); # OK no MyPragma qw(foo); # unimports foo no MyPragma; # unimports bar and baz no Method::Lexical; # unimports quux }
Lexical methods must be defined before any invocations of those methods are compiled, otherwise those invocations will be compiled as ordinary method calls. This won't work:
sub public { my $self = shift; $self->private(); # not a private method; compiled as an ordinary (public) method call } use Method::Lexical private => sub { ... };
This works:
use Method::Lexical private => sub { ... }; sub public { my $self = shift; $self->private(); # OK }
Method calls on glob or filehandle invocants are interpreted as ordinary method calls.
The method resolution order for lexical method calls on pre-5.10 perls is currently fixed at depth-first search.
0.30
mysubs
Sub::Lexical
Class::Fields
chocolateboy <chocolate@cpan.org>
Copyright (C) 2009-2013 by chocolateboy
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.8 or, at your option, any later version of Perl 5 you may have available.
To install Method::Lexical, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Method::Lexical
CPAN shell
perl -MCPAN -e shell install Method::Lexical
For more information on module installation, please visit the detailed CPAN module installation guide.