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instantiate objects from non-Catalyst model classes with parameters

by tospo (Hermit)
on Jan 25, 2011 at 17:36 UTC ( #884190=perlmeditation: print w/replies, xml ) Need Help??

This is another one in my series: I post this here in case I forget how I did it last time... :-)

I just had the following problem in my Catalyst app:
As a model I am using a class that has nothing to do with the Catalyst app itself. I want to instantiate objects of this class once per request, so I extend Catalyst::Model::Factory::PerRequest like this (my class needs its parameters to "new" in list form, not hashref):

package MyApp::Model::ProblemSolver; use Moose; use namespace::autoclean; extends 'Catalyst::Model::Factory::PerRequest'; __PACKAGE__->config( class => 'MyNonCatalyst::ProblemSolver', ); # provide arguments as a list instead of hash-ref sub mangle_arguments { my ($self, $args) = @_; return %$args; }

Now, objects of the MyNonCatalyst::ProblemSolver class need some parameters that go well in the app's config file, e.g. details for a database connection. It also needs parameters that will depend on input from the user of the site.
I found out that I can add this to the above model class (this is using the Moose way of overriding a parent's method and calling SUPER):

override 'prepare_arguments' => sub { my ($self, $c) = @_; my $config_params = super(); my $passed_in_params = $c->stash->{problem_solver_args}; my %merged_args = ( %$config_params, %$passed_in_params ); return \%merged_args; }; # prepare_arguments
This will merge the parameters from the config file and those that were passed in from the controller in such a way that the controller arguments override the config defaults. In my controller I can now do something like this:
$c->stash->{problem_solver_args}{some_param} = $user_input1 if $user_i +nput1; $c->stash->{problem_solver_args}{some_other_param} = $user_input2; my $problem_solver = $c->model('ProblemSolver'); my $result = $problem_solver->solve_problem();
in my my_app.yaml config file for the app I have:
Model::ProblemSolver: args: database: a_database_of_solved_problems some_param: SOME_DEFAULT_VALUE
This means that the database name is always taken from the app's config file but 'some_param' will be taken from user input if there is any or the above default is used to instantiate an object of the model class.

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Re: instantiate objects from non-Catalyst model classes with parameters
by ruoso (Curate) on Jan 29, 2011 at 10:29 UTC

    interesting you mention this. I have just wrote a model factory based on Catalyst::Component::InstancePerContext...

    package Leilao::Model::Negocio; use Moose; extends 'Catalyst::Model'; use namespace::autoclean; use Module::Find; use Module::Load; use Sub::Name; use Catalyst::Component::InstancePerContext; use Moose::Meta::Class; sub BUILD { my ($self) = @_; my @modules = findallmod 'Leilao::Negocio'; foreach my $neg (@modules) { load $neg; (my $mod = $neg) =~ s/^Leilao::Negocio/Leilao::Model::Negocio/ +; my $sub = sub { my ($self, $c) = @_; return $neg->new ( #user => $c->user, schema => $c->model('DB')->schema ); }; my $class = Moose::Meta::Class->create( $mod, superclasses => +['Catalyst::Model']); $class->add_method(build_per_context_instance => $sub); Catalyst::Component::InstancePerContext->meta->apply($class); } } __PACKAGE__->meta->make_immutable; 1;

    This model will use create adapted models for every class in the Leilao::Negocio namespace using Catalyst::Component::InstancePerContext and initializing the classes with arbitrary parameters.

    daniel

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