Client

Connecting to a Server

A client can be instantiated by using the Client object

client = Client("https://countries.trevorblades.com")

If only the endpoint is suppplied, the ws_endpoint (used for subscriptions) is assumed to be the same with "http" replaced by "ws".

Headers can be passed in a dictionary to the headers keyword argument, enabling things like authorisation tokens. These headers are used directly in the HTTP requests to the server.

client = Client(
    "https://myurl.com/queries",
    "wss://myurl.com/subscriptions",
    headers = Dict("Authorization" => "Bearer XXX"),
)

By default, when instantiated GraphQLClient will introspect the schema of the server and populate several fields of the Client object.

Global Client

A client can be set as the global client, which means that queries and other operations do not need the client passing as an argument.

global_graphql_client(Client("https://countries.trevorblades.com"))

The global client can then be accessed by the same function

julia> global_graphql_client()
GraphQLClient Client
       endpoint: https://countries.trevorblades.com
    ws_endpoint: wss://countries.trevorblades.com

Introspection

What needs introspection?

The following functionality requires introspection, and will attempt to introspect the client if it has not already been done so

• Functions to view operations (see below)
• query, mutate and open_subscription
  • check that the operation exists
  • use schema to build variables strings for arguments
• query - build output_fields if none supplied to function
• Type Introspection

The following functionality does not need introspection

• GraphQLClient.execute

Introspection is an incredibly powerful feature of GraphQL, and we hope to add more functions that make use of the informaton available in the schema.

Viewing Operations

The queries, mutations and subscriptions available from a server can be accessed by the following functions, which will all attempt to introspect the server if it has not already been completed.

get_queries(client)
get_mutations(client)
get_subscriptions(client)

Client Fields

There are several fields of Client that contain information relating to the schema. Whilst part of the private interface and therefore changes may occur outside of semantic versioning (in particular the format of this information may be changed to be more concretely typed), it can be accessed. If you have the need to ensure that this information can be accessed as part of the public interface, and therefore subject to semantic versioning, please open an issue.