Gennadiy Filatov

NAME

Salvation::Service::View - Base class for a view

SYNOPSIS

 package YourSystem::Services::SomeService::Defaults::V;

 use Moose;

 extends 'Salvation::Service::View';

 no Moose;

DESCRIPTION

Applied roles

Salvation::Roles::ServiceReference

REQUIRES

Moose

METHODS

To be called

process

 $view_instance -> process();

Processes service's DataSet with $view_instance and sets a Salvation::Service::View::Stack instance, or an ArrayRef of those instances (depending on MULTINODE result), to view_output attribute of appropriate Salvation::Service::State instance, returning the value being set.

process_node

 $view_instance -> process_node( $object );
 $view_instance -> process_node( $object, \@template );

Processes $object with $view_instance using \@template and returns Salvation::Service::View::Stack instance. @template could containt anything main's returning value could containt. Default @template contents are main's returning value' contents.

To be redefined

You can redefine following methods to achieve your own goals.

MULTINODE

Should return boolean value. Tells the view if it needs to process and return many rows returned by DataSet, or just one. The only argument is $self which is current view's instance. Default value is false.

main

Should return an ArrayRef containing template data which will be used to process objects.

Each element of an ArrayRef could be either of the following:

Non-reference scalar

A text which is interpreted as the type of each column listed in an ArrayRef which follows this text, if any. Example usage:

 regular_database_column => [
        'id',
        'name'
 ]

Having this, the view knows which methods of the model it needs to call in order to process each column.

ArrayRef

A list of column specs. Each element of such ArrayRef will be translated to model's method call. Each element of an ArrayRef could be either of the following:

Non-reference scalar

A text which is interpreted as the name of the column. Here an appropriate model's method call is happening.

In example, having an element named id and column type already set to regular_database_column, the view will generate model's method name like this:

 my $type   = 'regular_database_column';
 my $column = 'id';

 my $model_method = sprintf(
        '%s_%s',
        $type,
        $column
 );

Then the view will check if the model can( $model_method ) and, if it is true, will call this method with an $object argument where the $object is the object being processed right now.

However, if the check returned false, the view will try to generate another method name like this:

 my $another_model_method = sprintf(
        '__%s',
        $type
 );

Then the view will check if the model can( $another_model_method ) and, if it is true, will call this method with two arguments: $object and $column where the $object is the object being processed right now and the $column is the name of current column.

HashRef

Advanced column spec. Should contain one key and one value where key is the plain column name and the value is the HashRef which will be interpreted as column modifiers.

Example:

 some_type => [
        'id',
        { column => \%modifiers }
 ]

Column modifiers could be:

constraint

A CodeRef which will be called in order to check whether the column needs to be processed, or needs to be skipped. Should return boolean value.

 constraint => sub
 {
        my ( $view_instance, $object_being_processed, $service_args ) = @_;

        return ( int( rand( 2 ) ) == 1 );
 }

$service_args is the returning value of view's service's args method.

nocache

A boolean value.

By default, the view will try to calculate a value for current column using probably light model's method which name is generated like this:

 sprintf(
        '__%s',
        $type
 )

Then the view will use this value in couple with the column's name and a few other parameters to produce some unique key.

Then the view will check its cache using Salvation::Service::View::SimpleCache and if there is a value - this value will be used immediately as the column's value, skipping all the calculations described above.

But if the cache has no value for the key - this value will appear in the cache after all further calculations will be done, and will be reused if there will be a request to do the same calculations.

So yes, if the nocache modifier is set to true - there will be no cache usage for such column.

skip_false

A boolean value. If set to true, the column will not be included in the output if it has the value equivalent to PERL's false. Default value is false.

sticky

As the opposite of skip_false, sticky guarantees that the column will be included in the output even if it's value is equivalent to PERL's false and skip_false is set to true.

If the key sticky exists in column modifiers list - it is true, otherwise it is false.

CodeRef

It will be executed for every object which is being processed with following arguments:

$self

Current view's instance.

$object

An object being processed.

$args

Returning value of view's service's args method.

Returning value should be a HashRef containing arguments to the new method of Salvation::Service::View::Stack::Frame.