NAME

Class::DispatchToAll - DEPRECATED - dispatch a method call to all inherited methods

VERSION

version 0.13

SYNOPSIS

  DEPRECATED - Do not use this module anymore!

  package My::Class;
  our @ISA=qw(SomeClass SomeOtherClass More::Classes);
  use Class::DispatchToAll qw(dispatch_to_all);

  my $self=bless {},My::Class  # not a proper constructor, I know..

  # this calls 'some_method' in all Classes My::Class inherits from
  # and all classes those classes inherit from, and all ... you get
  # the point.
  $self->dispatch_to_all('some_method');

  # saves all return values from all calls in an array
  my @returns=$self->dispatch_to_all('some_method');

DESCRIPTION

DEPRECATED - Do not use this module anymore!

But here are the old docs, anyway:

See the Docs of Damian Conways Module Class::Delegation for a good introduction about Dispatching vs. Inheritance.

Class::DispatchToAll enables you to call all instantances of a method in your inheritance tree (or labyrinth..).

The standard Perl behaviour is to call only the lefternmost instance it can fing doing a depth first traversial.

Imagine the following class structure:

              C
             /
   A    B  C::C
    \  / \ /
   A::A   D
       \ /
     My::Class

Perl will try to find a method in this mess in this order:

 My::Class -> A::A  ->  A  ->  B  ->  D  -> B  -> C::C -> C

(Note that it will look twice in B because B is a parent of both A::A and D))

As soon as Perl finds the method somewhere, it will short-circuit out of it's search and invoke the method.

And that is exactly the behaviour Class::DispatchToAll changes.

If you use dispatch_to_all (provided by Class::DispatchToAll) to call your method, Perl will look in all of the aforementioned packages and run all the methods it can find. It will even collect all the return values and return them to you as an array, if you want it too.

dispatch_to_all

Call it either as a function:

  dispatch_to_all($self,
                  $method_to_call,
                  \%attribs,
                  @params_passed_to_method);

or as a method

  $self->dispatch_to_all($method_to_call,
                         \%attribs,
                         @params_passed_to_method);

• $self is the object you want the method to be invoked on

• $method_to_call is the name of the method to be called

  Eg. instead of $self->do_something say $self->dispatch_to_all('do_something')

• %attribs is an optional hash (has to be passed by reference) of attributes to alter Class:DispatchToAlls behaviour. If you want to pass arguments to the methods but do not want to set any attributes, you have to pass undef (c.f. the way DBH->do($query,undef,@bind_params) works, if you know it..)

  Currently there is only one attribute implemented:

  • no_collect

    set it to a true value, and the return values of the method calls won't be collected. This may save some memory and CPU over just discarding the return value of dispatch_to_all.

• @params_passed_to_method will be passed to the methods as is.

If you didn't set no_collect, dispatch_to_all will return an array or ARRAYREF (depending on what you were calling for, so watch your context) where each element is the return value of a method. (NOTA BENE: If one method returns more than one value, this might lead to some confusion.. See TODO).

Currently, the first called method (i.e. the one Perl would originally call) will be the first value of this array, followed by all other values. If a method doesn't exist in any class, no value will be returned (maybe undef would be better, don't know now..).

What you do with this values and how to decide which one to use (if you only need one) is up to you.

One thing I do (and the reason for writing this module) is to condensate different config values to one, e.g.:

  A::config="test";
  A::A::config="test2";
  My::Class::config="test3";

  # assuming a method get_config not implemented in this example
  print join(",",@{$self->dispatch_to_all('get_config')});
  # prints: test3,test2,test

Or this, merging a hash:

  A::hash={foo=>'foo'};
  C::hash={bar=>'bar'};
  A::A::hash={foo=>'FOO'};
  My::Class::hash={even=>'more'};

  # assuming a method get_hash not implemented in this example
  my @v=$self->dispatch_to_all('get_hash');
  my %hash=();
  foreach (reverse @v) {
      %hash=(%hash,%$_);
  }

  # %hash now looks like: { foo=>'FOO', # from A::A, overriding A
  # bar=>'bar', # from C even=>'more', # from My::Class }

Please note the reverse. This enables the overriding of values "further away" from the calling class by values that are "nearer"

See the test script for more examples.

TODO

• handling of methods that return more than one value

• different methods of traversal (right to left, width before depth)

• preventing multiple access to the same method (caused by a "diamond" class hierarchy)

SEE ALSO

Class::Delegation, NEXT

This thread on perlmonks: http://www.perlmonks.org/index.pl?node_id=180852

AUTHOR

Thomas Klausner <domm@plix.at>

COPYRIGHT AND LICENSE

This software is copyright (c) 2001 - 2006 by Thomas Klausner.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.