How to implement graphql subscription using apollo ios client

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

Answer 1

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": "", "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:///v1alpha1/graphql"
        let graphQLSubscriptionEndpoint = "ws:///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("", 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.