Some GraphQL features use unique IDs to load objects:
node(id:) field looks up objects by IDloads: configurations look up objects by IDTo use these features, you must provide a function for generating UUIDs and fetching objects with them. In your schema, define self.id_from_object and self.object_from_id:
class MySchema < GraphQL::Schema
def self.id_from_object(object, type_definition, query_ctx)
# Generate a unique string ID for `object` here
# For example, use Rails' GlobalID library (https://github.com/rails/globalid):
object.to_gid_param
end
def self.object_from_id(global_id, query_ctx)
# For example, use Rails' GlobalID library (https://github.com/rails/globalid):
GlobalID.find(global_id)
end
end
SQIDs are an alternative to
to_gid_paramwhich generate shorter IDs. Here is a detailed guide of how they can be used.
One requirement for Relay’s object management is implementing the "Node" interface.
To implement the node interface, add GraphQL::Types::Relay::Node to your definition:
class Types::PostType < GraphQL::Schema::Object
# Implement the "Node" interface for Relay
implements GraphQL::Types::Relay::Node
# ...
end
To tell GraphQL how to resolve members of the Node interface, you must also define Schema.resolve_type:
class MySchema < GraphQL::Schema
# You'll also need to define `resolve_type` for
# telling the schema what type Relay `Node` objects are
def self.resolve_type(type, obj, ctx)
case obj
when Post
Types::PostType
when Comment
Types::CommentType
else
raise("Unexpected object: #{obj}")
end
end
end
Nodes must have a field named "id" which returns a globally unique ID.
To add a UUID field named "id", implement the GraphQL::Types::Relay::Node interface::
class Types::PostType < GraphQL::Schema::Object
implements GraphQL::Types::Relay::Node
end
This field will call the previously-defined id_from_object class method.
node field (find-by-UUID)You should also provide a root-level node field so that Relay can refetch objects from your schema. You can attach it like this:
class Types::QueryType < GraphQL::Schema::Object
# Used by Relay to lookup objects by UUID:
# Add `node(id: ID!)
include GraphQL::Types::Relay::HasNodeField
# ...
end
nodes fieldYou can also provide a root-level nodes field so that Relay can refetch objects by IDs:
class Types::QueryType < GraphQL::Schema::Object
# Fetches a list of objects given a list of IDs
# Add `nodes(ids: [ID!]!)`
include GraphQL::Types::Relay::HasNodesField
# ...
end