graphql-example.pl

#!perl

use 5.014;
use warnings;

use GraphQL::Schema;
use GraphQL::Execution qw/execute/;

use Data::Dumper;

package Person {
    use Moo; # GraphQLがMoo依存なので使わせてもらう

    has name => (
        is       => 'ro',
        required => 1, 
    );

    has favorite_fruit_ids => (
        is       => 'ro',
        required => 1,
    );
};

package Fruit {
    use Moo;

    has id => (
        is       => 'ro',
        required => 1,
    );

    has name => (
        is       => 'ro',
        required => 1, 
    );
};

package MyApp::GraphQL::Resolver::Query {
    sub person {
        my ($root_value, $args, $context, $info) = @_;
        my $person = main::get_person();
        return { name => $person->name, favorite_fruit_ids => $person->favorite_fruit_ids };
    }
};

package MyApp::GraphQL::Resolver::Person {
    sub favoriteFruits {
        my ($root_value, $args, $context, $info) = @_;
        my $fruits = main::get_fruits($root_value->{favorite_fruit_ids});
        return [ map +{ name => $_->name }, @$fruits ];
    }
};

my $idx = 1;
my @fruits = map { Fruit->new(id => $idx++, name => $_) } qw/apple banana orange grape kiwifruit/;
my $person = Person->new(name => 'taiyoh', favorite_fruit_ids => [1, 5]);

sub get_person { $person }
sub get_fruits {
    my $ids = shift;
    my %id_map = map { $_ => 1 } @$ids;
    return [ grep { $id_map{$_->id} } @fruits ];
}

my $schema = GraphQL::Schema->from_doc(<<'EOF');
type Person {
    name: String!
    favoriteFruits: [Fruit!]!
}

type Fruit {
    name: String!
}

type Query {
    person: Person
}

schema {
    query: Query
}
EOF

my $query = <<'EOQ';
{
    person {
        name
        favoriteFruits {
            name
        }
    }
}
EOQ

my $res = execute(
    $schema,
    $query,
    {}, # root_value
    {}, # context_value
    {}, # variables
    undef, # operation_name,
    sub { # resolver
        my ($root_value, $args, $context, $info) = @_;
        my $field_name  = $info->{field_name};
        my $parent_type = $info->{parent_type}->name;

        my $pkg = sprintf('MyApp::GraphQL::Resolver::%s', $parent_type);
        if (my $resolver = $pkg->can($field_name)) {
            return $resolver->($root_value, $args, $context, $info);
        }
        # https://metacpan.org/source/ETJ/GraphQL-0.26/lib/GraphQL/Execution.pm#L668-688 より
        my $root_ref = ref $root_value;
        if ($root_ref eq 'CODE') {
            return $root_value->($args, $context, $info);
        } elsif ($root_ref ne 'HASH' && $root_value->can($field_name)) {
            return $root_value->$field_name($args, $context, $info);
        }
        return $root_value->{$field_name};
    }
);

local $Data::Dumper::Indent = 1;
say Dumper($res);

__END__
$VAR1 = {
  'data' => {
    'person' => {
      'favoriteFruits' => [
        {
          'name' => 'apple'
        },
        {
          'name' => 'kiwifruit'
        }
      ],
      'name' => 'taiyoh'
    }
  }
};