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DCI for perl
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lib
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README

README

NAME
    DCI - Collection of utilities for writing perl code that fits the DCI
    methodology.

DESCRIPTION
    The DCI concept was created by Trygve Reenskaug, (inventor of MVC) and
    James Coplien.

    DCI Stands for Data, Context, Interactions. It was created to solve the
    problem of unpredictable emergent behavior in networks of interacting
    objects. This problem shows itself in complex OOP projects, most
    commonly in projects with deep polymorphism. This is a problem that
    Procedural/Imperative Programming does not have.

    DCI does not replace OOP, instead it augments it with lessons learned
    from looking back at Procedural Programming. It defines a way to
    encapsulate use cases into a single place. This provides an advantage to
    the programmer by reducing the number of interactions that need to be
    tracked. Another advantage is the reduction of side-effects between
    contexts.

    Another way to look at it is that a DCI implementation is much more
    maintainable as a project matures. Changes to requirements and
    additional features cause clean OOP project to degrade into spaghetti.
    DCI on the other hand maintains code clarity under changing
    requirements.

MORE ABOUT DCI
    Look at DCI::Introduction for a complete introduction into DCI concepts.

SYNOPSIS
    This synopsis is very basic, see individual modules for better
    module-specific examples. Also see DCI::Introduction if you do not yet
    understand DCI concepts.

  DUMB DATA CLASS
        package Test::Data;
        use strict;
        use warnings;

        sub new {
            my $class = shift;
            my ( $value ) = @_;
            return bless( \$value, $class );
        }

        sub get_text { ${ $_[0] } }

        sub set_text { 
            my $self = shift;
            my ( $new_val ) = @_;
            $$self = $new_val;
        }

        1;

  TRIVIAL CAST CLASS (ROLE)
        package Test::Cast;
        use strict;
        use warnings;

        use DCI qw/Cast/;

        # Delegate the text() method to the 'core'
        delegate qw/text/;

        # Restrict core to being a Test::Data object.
        require_core qw/Test::Data/;

        # Generate some accessors which keep state in the Cast, but do not interfer
        # with the Core object.
        accessors qw/cache/;

        # Add a method to our cast
        sub render {
            my $self = shift;

            my $cached = $self->cache;

            # text() is delgated to the underlying 'core'
            $cached = $self->cache(
                "The text is: '" . $self->text() . "'\n"
            ) unless $cached;

            return $cached;
        }

        1;

  A CONTEXT
        package Test::Context;
        use strict;
        use warnings;

        use DCI qw/Context/;
        use Test::Cast;

        # Declare some required member objects
        cast first => 'Test::Cast',
             last  => 'Test::Cast';

        # export a function named 'quick_render' that constructs the object from
        # arguments, and returns the result of running the 'render()' method on the
        # created object.
        sugar quick_render => (
            method  => 'render',
            ordered => [qw/ first last /]
        );

        # A sugar export that takes named arguments.
        sugar parametric_render => 'render';

        # Method we use to kick-off the encapsulated task of the Context.
        sub render { shift->first->render }

        1;

  PUTTING IT ALL TOGETHER
        use Test::More;

        use Test::Context qw/quick_render/;

        is(
            quick_render( "String A", "String B" ),
            "The text is: 'String A'\nThe text is: 'String B'",
            "Rendered first and last strings using quick sugar"
        );

        is(
            parametric_render(
                first => "String A",
                last  => "String B",
            ),
            "The text is: 'String A'\nThe text is: 'String B'",
            "Rendered first and last strings using named parameters"
        );

        my $it = Test::Context->new(
            first => "String A",
            last  => "String B",
        );

        is(
            $it->render,
            "The text is: 'String A'\nThe text is: 'String B'",
            "Rendered first and last strings from onbject instance"
        );

        1;

OBJECT TYPES
  CONTEXT
   SUGAR FUNCTIONS
    See DCI::Meta::Context which actually exports the sugar.

   METHODS
    See DCI::Context the base class for all Casts.

  CAST
   SUGAR FUNCTIONS
    See DCI::Meta::Cast which actually exports the sugar.

   METHODS
    See DCI::Cast the base class for all Casts.

API STABILITY
    Versions below 0.011 were a prototype, the API was subject to flux. For
    0.011 the API has been completely re-written using the lessons learned
    from the old API.

    As of 0.011, the API can be considered stable. This means that changes
    which break backwards compatibility will be few and far between.

SEE ALSO
    DCI::Meta::Context
        Meta class for contexts

    DCI::Meta::Cast
        Meta class for casts

    DCI::Context
        Base class for contexts

    DCI::Cast
        Base class for casts

ACHNOWLEDGEMENTS
    The DCI concept was created by Trygve Reenskaug, (inventor of MVC) and
    James Coplien.

AUTHORS
    Chad Granum exodist7@gmail.com

COPYRIGHT
    Copyright (C) 2011 Chad Granum

    DCI is free software; Standard perl licence.

    DCI is distributed in the hope that it will be useful, but WITHOUT ANY
    WARRANTY; without even the implied warranty of MERCHANTABILITY or
    FITNESS FOR A PARTICULAR PURPOSE. See the license for more details.

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