NAME

GraphQL::Subscription - Implement GraphQL subscriptions

SYNOPSIS

use GraphQL::Subscription qw(subscribe);
my $result = subscribe($schema, $doc, $root_value);

DESCRIPTION

Implements a GraphQL "subscription" - a feed of events, commonly of others' mutations.

METHODS

subscribe

my $result = subscribe(
  $schema,
  $doc, # can also be AST
  $root_value,
  $context_value,
  $variable_values,
  $operation_name,
  $field_resolver,
  $promise_code,
  $subscribe_resolver,
);

Takes the same args as "execute" in GraphQL::Execution, except that the $promise_code is mandatory, and there is the optional $subscribe_resolver which, supplied or not, will be used instead of the $field_resolver to resolve the initial subscription. The $field_resolver will still be used for resolving each result.

Returns a promise of either:

• an error result if the subscription fails (generated by GraphQL)

• a GraphQL::AsyncIterator instance generated by a resolver, probably hooked up to a GraphQL::PubSub instance

The event source returns values by using "publish" in GraphQL::AsyncIterator. To communicate errors, resolvers can throw errors in the normal way, or at the top level, use "error" in GraphQL::AsyncIterator.

The values will be resolved in the normal GraphQL fashion, including that if there is no specific-to-field resolver, it must be a value acceptable to the supplied or default field-resolver, typically a hash-ref with a key of the field's name.