How to implement graphql subscription using apollo ios client - graphql

Question

I am trying to implement graphql subscription using apollo ios client. But not able to figure it out as lack of documentation examples.
Example given on apollo documentation is:
let apollo: ApolloClient = {
let configuration = URLSessionConfiguration.default
// Add additional headers as needed
configuration.httpAdditionalHeaders = ["Authorization": "Bearer <token>"] // Replace `<token>`
let url = URL(string: "http://localhost:8080/graphql")!
return ApolloClient(networkTransport: HTTPNetworkTransport(url: url, configuration: configuration))
}()
APOLLO IOS GUIDE: Creating a client

Answer 1

Implement the subscription in apollo ios graphql client by following below steps.
Using cocoapods:
pod 'Apollo'
pod 'Apollo/WebSocket'
pod install
To create client to support subscription and authentication. Add below code in AppDelegate.swift:
Websocket - we have to use WebSocketTransport and URLRequest
Authentication - we have to pass auth parameters in connection params connectingPayload to server. And for http we are passing it in headers as mentioned in question snippet.
SplitNetworkTransport- To combine both http and websocket to create client. we have to use httpNetworkTransport and webSocketNetworkTransport
lazy var apollo: ApolloClient = {
let authPayloads = [
"Authorization": "Bearer "
]
let configuration = URLSessionConfiguration.default
configuration.httpAdditionalHeaders = authPayloads
let map: GraphQLMap = authPayloads
let wsEndpointURL = URL(string: "ws://localhost:8080/subscriptions")!
let endpointURL = URL(string: "http://localhost:8080/api")!
let websocket = WebSocketTransport(request: URLRequest(url: wsEndpointURL), connectingPayload: map)
let splitNetworkTransport = SplitNetworkTransport(
httpNetworkTransport: HTTPNetworkTransport(
url: endpointURL,
configuration: configuration
),
webSocketNetworkTransport: websocket
)
return ApolloClient(networkTransport: splitNetworkTransport)
}()

Answer 2

I'm getting close. I was getting rejected for not having the correct headers in my Websocket upgrade. I ended up having to set them directly on the URLRequest object.
var apollo: ApolloClient? {
let authHeaders = ["X-Hasura-Access-Key": "<my_Key>", "Content-Type": "application/json"]
let configuration = URLSessionConfiguration.default
// Add additional headers as needed
configuration.httpAdditionalHeaders = authHeaders
//The string to my graph QL Server run by Hasure on AWS RDS.
let graphQLEndpoint = "http://<my_host>/v1alpha1/graphql"
let graphQLSubscriptionEndpoint = "ws://<my_host>/v1alpha1/graphql"
//Take my Ec2 Server string and make a URL for the graph QL and subscriptions
guard let httpURL = URL(string: graphQLEndpoint), let webSocketURL = URL(string: graphQLSubscriptionEndpoint) else {
return nil
}
let httpTransport = HTTPNetworkTransport(url: httpURL, configuration: configuration, sendOperationIdentifiers: false)
var request = URLRequest(url: webSocketURL)
request.setValue("<my_key>", forHTTPHeaderField: "X-Hasura-Access-Key")
request.setValue("application/json", forHTTPHeaderField: "Content-Type")
let webSocketTransport = WebSocketTransport(request: request, sendOperationIdentifiers: false, connectingPayload: nil)
let splitTransport = SplitNetworkTransport(httpNetworkTransport: httpTransport, webSocketNetworkTransport: webSocketTransport)
//Initalize the APolloClient with that URL.
return ApolloClient(networkTransport: splitTransport)
}
The upgrade worked after that.

Answer 3

Here's my ApolloClient setup for just a web socket transport client:
let connectingPayload = ["authToken": accessToken]
let urlRequest = URLRequest(url: baseURL)
let webSocketTransport = WebSocketTransport(request: urlRequest, sendOperationIdentifiers: false, connectingPayload: connectingPayload)
let apollo = ApolloClient(networkTransport: webSocketTransport)