NAME

Object::Lazy - create objects late from non-owned classes

VERSION

0.06

SYNOPSIS

    use Foo 123; # because the class of the real object is Foo, version could be 123
    use Object::Lazy;

    my $foo = Object::Lazy->new(
        sub{
            return Foo->new();
        },
    );

    bar($foo);

    sub bar {
        my $foo = shift;

        if ($condition) {
            # a foo object will be created
            print $foo->output();
        }
        else {
            # foo object is not created
        }

        return;
    }

To combine this and a lazy use, write somthing like that:

    use Object::Lazy;

    my $foo = Object::Lazy->new(
        sub{
            my $code = 'use Foo 123';
            eval $code;
            $@ and die "$code $@";
            return Foo->new();
        },
    );

    # and so on

Read topic SUBROUTINES/METHODS to find the entended constructor and all the optional parameters.

EXAMPLE

Inside of this Distribution is a directory named example. Run this *.pl files.

DESCRIPTION

This module implements 'lazy evaluation' and can create lazy objects from every class.

Creates a dummy object including a subroutine which knows how to build the real object.

Later, if a method of the object is called, the real object will be built.

Method isa and method can is implemented.

SUBROUTINES/METHODS

method new

short constructor

    $object = Object::Lazy->new(sub{
        return RealClass->new(...);
    });

extended constructor

    $object = Object::Lazy->new({
        build => sub {
            return RealClass->new(...);
        },
    });

• optional parameter isa

  There are 3 ways to check the class or inheritance.

  If there is no parameter isa, the object must be built before.

  If the use RealClass; is outside of build = sub {...}> then the class method RealClass-isa(...);> checks the class or inheritance.

  Otherwise the isa parameter is a full notation of the class and possible of the inheritance.

      $object = Object::Lazy->new({
          ...
          isa => 'RealClass',
      });

  or

      $object = Object::Lazy->new({
          ...
          isa => [qw(RealClass BaseClassOfRealClass)],
      });

• optional parameter logger

  Optional notation of the logger code to show the build process.

      $object = Object::Lazy->new({
          ...
          logger => sub {
              my $at_stack = shift;
              print "RealClass at_stack";
          },
      });

• optional parameter ref

  Optional notation of the ref answer.

  It is not a good idea to use the Object::Lazy::Ref module by default. But there are situations, the lazy idea would run down the river if I had not implemented this feature.

      use Object::Lazy::Ref; # overwrite CORE::GLOBAL::ref
  
      $object = Object::Lazy->new({
          ...
          ref => 'RealClass',
      });
  
      $boolean_true = ref $object eq 'RealClass';

method isa

If no isa parameter was given at method new, the object will build.

Otherwise the method isa checks by isa class method or only the given parameters.

    $boolean = $obejct->isa('RealClass');

or

    $boolean = $obejct->isa('BaseClassOfRealClass');

method can

The object will build. After that the can method checks the built object.

    $coderef_or_undef = $object->can('method');

DIAGNOSTICS

The constructor can confess at false parameters.

CONFIGURATION AND ENVIRONMENT

nothing

DEPENDENCIES

Carp

English

Object::Lazy::Validate

INCOMPATIBILITIES

not known

BUGS AND LIMITATIONS

not known

SEE ALSO

Data::Lazy The scalar will be built at my $scalar = shift; at first sub call.

Scalar::Defer The scalar will be built at my $scalar = shift; at first sub call.

Class::LazyObject No, I don't write my own class/package.

Object::Realize::Later No, I don't write my own class/package.

Class::Cache There are lazy parameters too.

Object::Trampoline This is nearly the same idea.

Objects::Collection::Object Object created at call of method isa.

AUTHOR

Steffen Winkler

LICENSE AND COPYRIGHT

Copyright (c) 2007 - 2009, Steffen Winkler <steffenw at cpan.org>. All rights reserved.

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

cpanm Object::Lazy

perl -MCPAN -e shell
install Object::Lazy