Bread::Board::Manual::Concepts::Typemap - An overview of the typemapping feature

       Stevan Little <stevan@iinteractive.com>

       Please report any bugs or feature requests on the bugtracker website
       https://github.com/stevan/BreadBoard/issues

       When submitting a bug or request, please include a test-file or a patch to an existing test-file that
       illustrates the bug or desired feature.

       This example should give a good basic overview of this feature and more details can be found in the test
       suite (t/07*.t). These show examples of how to typemap roles to concrete classes and how to supply hints
       to "infer" to help Bread::Board figure out specific details.

       As I mentioned above, this feature should be considered experimental and we are still working out details
       and writing tests for it. Any contributions are welcome.

       This software is copyright (c) 2019, 2017, 2016, 2015, 2014, 2013, 2011, 2009 by Infinity Interactive.

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

perl v5.36.0                                       2022-12-12              Bread::Board::...ncepts::Typemap(3pm)

       A new (read: experimental) feature of Bread::Board is typemapped services.  These are services which are
       mapped to a particular type rather then just a name. This feature has the potential to make obsolete a
       large amount of the Bread::Board configuration by simply asking Bread::Board to figure things out on its
       own. Here is a small example of how this works.

         # define the classes making sure
         # to specify required items and
         # their types

         {
             package Stapler;
             use Moose;

             package Desk;
             use Moose;

             package Chair;
             use Moose;

             package Cubicle;
             use Moose;

             has 'desk'  => ( is => 'ro', isa => 'Desk',  required => 1 );
             has 'chair' => ( is => 'ro', isa => 'Chair', required => 1 );

             package Employee;
             use Moose;

             has [ 'first_name', 'last_name' ] => (
                 is       => 'ro',
                 isa      => 'Str',
                 required => 1,
             );

             has 'stapler' => ( is => 'rw', isa => 'Stapler', predicate => 'has_stapler' );

             has 'work_area' => ( is => 'ro', isa => 'Cubicle', required => 1 );
         }

         # now create the container, and
         # map the Employee type and ask
         # Bread::Board to infer all the
         # other relationships

         my $c = container 'Initech' => as {
             typemap 'Employee' => infer;
         };

         # now you can create new Employee objects
         # by calling ->resolve with the type and
         # supplying the required parameters (see
         # below for details).

         my $micheal = $c->resolve(
             type       => 'Employee',
             parameters => {
                 first_name => 'Micheal',
                 last_name  => 'Bolton'
             }
         );

         my $cube = $micheal->work_area; # this will be a Cubicle object
         $cube->desk;  # this will be a Desk object
         $cube->chair; # this will be a Chair object

         $micheal->has_stapler; # this is false

         # We can create another Employee object
         # and this time we pass in the optional
         # parameter for the non-required 'stapler'
         # attribute

         my $milton = $c->resolve(
             type       => 'Employee',
             parameters => {
                 first_name => 'Milton',
                 last_name  => 'Waddams',
                 stapler    => Stapler->new
             }
         );

         $milton->has_stapler; # this is true

       In the above example, we created a number of Moose classes that had specific required relationships. When
       we called "infer" for the Employee object, Bread::Board figured out those relationships and set up
       dependencies and parameters accordingly.

       For the "work_area" object, we saw the Cubicle type and then basically called "infer" on the Cubicle
       object. We then saw the Desk and Chair objects and called "infer" on those as well.  The result of this
       recursive inference was that the Employee, Cubicle, Desk and Chair relationships were modeled in
       Bread::Board as dependent services.

       Bread::Board also took it one step further.

       We were able to resolve the Cubicle, Desk and Chair types automatically because they were already defined
       by Moose as subtypes of the Object type. We knew that it could introspect those classes and get more
       information. However, this was not the case with the first_name and last_name attributes of the Employee
       object.  In that case, we determined that we couldn't resolve those objects and (because it was a top-
       level inference) instead turned them into required parameters for the inferred Employee service.

       And lastly, with a top-level inference (not one caused by recursion) Bread::Board will also look at all
       the remaining non-required attributes and turn them into optional parameters. In this case we have a
       "stapler" attribute that is not required and so is listed as an optional parameter, meaning that it is
       not required, but still subject to type checking.

       Bread::Board::Manual::Concepts::Typemap - An overview of the typemapping feature

       version 0.37