---
name: "GraphQL::Subscription"
section: "3pm"
platform: "linux"
package: "libgraphql-perl"
version: "0.54-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/GraphQL::Subscription"
---

# GraphQL::Subscription(3pm)

Implement GraphQL subscriptions

## 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.