AppSync With Apollo(iOS)

Recently I met a problem.

1. For building a GraphQL Application that has a server with AWS AppSync, and Apollo SDK as client tool.
2. Ream-time is requrement so I will use GraphQL Subscription. By some reason can not use the Amplify of AWS.
3. Integrate them in an iOS client and test them.

---

There are 3 steps mainly:

1. Build server api by AppSync console.
2. Build client program and integrate Apollo in it.
3. Generate code about GraphQL in client, and test functionality.

Step1 and Step2 can be completed smoothly if following the official docs. But most problems are in step 3.

1. If codegen failed, it may be there wrong in the schema.json file.
2. Operation.graphql files are required by default.
3. Subscription
   1. Its endPoint is a little different and Query, mutation.
   2. Server that implementd sub protocal of GraphQL over Websocket Protocol may be different.
      • AppSync's server protocol is graphql-ws, so we need manually config that by Apollo SDK.
   3. Need customize a header in auth mode.
      • Header parameter format based on AWS AppSync API authorization mode
   4. Format of payload.

      • Format of payload in connection is different in Apollo SDK and AppSync,so we need fix that.

      • Appsync payload

        {
            "id": "subscriptionId",
            "type": "start",
            "payload":
            {
                "data":
                {
                    "query": "query stirng",
                    "variables": "variables"
                },
                "extensions":
                {
                    "authorization":
                    {
                        "host": "host",
                        "x-api-key": "apikey"
                    }
                }
            }
        }
        

      • Apollo payload

        {
            "id": "subscriptionId",
            "type": "start",
            "payload":
            {
                "variables": "variables",
                "extensions": "extensions",
                "operationName": "subscriptionName",
                "query": "quey string"
            }
        }
        

Because of something above, I customized a simple network class as a sample. It just contains some simple and required things.