grafbase_sdk

Trait ResolverExtension

Source 
pub trait ResolverExtension: Sized + 'static {
    // Required methods
    fn new(
        schema_directives: Vec<SchemaDirective>,
        config: Configuration,
    ) -> Result<Self, Error>;
    fn resolve_field(
        &mut self,
        headers: SubgraphHeaders,
        subgraph_name: &str,
        directive: FieldDefinitionDirective<'_>,
        inputs: FieldInputs<'_>,
    ) -> Result<FieldOutput, Error>;
    fn resolve_subscription(
        &mut self,
        headers: SubgraphHeaders,
        subgraph_name: &str,
        directive: FieldDefinitionDirective<'_>,
    ) -> Result<Box<dyn Subscription>, Error>;

    // Provided method
    fn subscription_key(
        &mut self,
        headers: &SubgraphHeaders,
        subgraph_name: &str,
        directive: FieldDefinitionDirective<'_>,
    ) -> Option<Vec<u8>> { ... }
}
Expand description

A trait that extends Extension and provides functionality for resolving fields.

Implementors of this trait are expected to provide a method to resolve field values based on the given context, directive, and inputs. This is typically used in scenarios where field resolution logic needs to be encapsulated within a resolver object, allowing for modular and reusable code design.

Required Methods§

Source

fn new( schema_directives: Vec<SchemaDirective>, config: Configuration, ) -> Result<Self, Error>

Creates a new instance of the extension.

§Arguments
  • schema_directives - List of all schema directives for all subgraphs defined in this extension.
  • config - The configuration for this extension, from the gateway TOML.
§Returns

Returns an instance of this resolver. Upon failure, every call to this extension will fail. Similar to how every request to a subgraph would fail if it went down.

Source

fn resolve_field( &mut self, headers: SubgraphHeaders, subgraph_name: &str, directive: FieldDefinitionDirective<'_>, inputs: FieldInputs<'_>, ) -> Result<FieldOutput, Error>

Resolves a GraphQL field, called at most once per occurrence in the query. If contained inside lists, this resolver may receive multiple inputs to resolve. So for a schema like:

ⓘ
type Query {
    users: [User]
}

type User {
    id: ID!
    field: JSON # <- field resolver by this extension
}

and a query like:

ⓘ
query {
   users {
      field
   }
}

This function will called at most once, independently of the number of users. FieldInputs will have an entry for every occurrence of said field within the response. So if there are 10 users, FieldInputs will contain 10 ResolverInput.

Any requested response data such as the user id will be included in the FieldInput, but every other directive argument that is either static or depends solely on the field arguments will be provided in the FieldDefinitionDirective.

The output of this function is fairly flexible, you can return individual elements/errors or everything batched together. The data may contain additional fields, they’ll be ignored. But it MUST have the proper shape and the appropriate names. The gateway will validate the every element.

§Arguments
  • headers - The subgraph headers associated with this field resolution
  • subgraph_name - The name of the subgraph associated with this field resolution
  • directive - The directive associated with this field resolution
  • definition - The field definition containing metadata
  • inputs - The input values provided for this field
§Returns

Returns a Result containing either the resolved FieldOutput value or an Error

Source

fn resolve_subscription( &mut self, headers: SubgraphHeaders, subgraph_name: &str, directive: FieldDefinitionDirective<'_>, ) -> Result<Box<dyn Subscription>, Error>

Resolves a subscription field by setting up a subscription handler.

§Arguments
  • headers - The subgraph headers associated with this field resolution
  • directive - The directive associated with this subscription field
  • definition - The field definition containing metadata about the subscription
§Returns

Returns a Result containing either a boxed Subscriber implementation or an Error

Provided Methods§

Source

fn subscription_key( &mut self, headers: &SubgraphHeaders, subgraph_name: &str, directive: FieldDefinitionDirective<'_>, ) -> Option<Vec<u8>>

Returns a key for a subscription field.

This method is used to identify unique subscription channels or connections when managing multiple active subscriptions. The returned key can be used to track, manage, or deduplicate subscriptions.

§Arguments
  • headers - The subgraph headers associated with this subscription
  • subgraph_name - The name of the subgraph associated with this subscription
  • directive - The directive associated with this subscription field
§Returns

Returns an Option<Vec<u8>> containing either a unique key for this subscription or None if no deduplication is desired.

Dyn Compatibility§

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors§