未触发AWS AppSync iOS SDK订阅

Question

使用iOS SDK时无法启动我的AWS AppSync订阅。我已经成功运行了Mutations and Queries，因此我不确定订阅可能会做错什么。

我的AppSync GraphQL架构。我已经确认所有这些都可以在AWS AppSync控制台中正常工作。

type Mutation {
    updateState(id: ID!, state: State!): StateChange
}

type Subscription {
    watchState(id: ID!): StateChange
        @aws_subscribe(mutations: ["updateState"])
}

type StateChange {
    id: ID!
    state: State!
}

enum State {
    regular
    lockdown
    accolades
}

我的iOS代码：

        //Set a variable to discard at the class level
        var discard: Cancellable?

        //In your app code
        do {
            discard = try appSyncClient?.subscribe(subscription: WatchStateSubscription(id: "20"),
 resultHandler: { (result, transaction, error) in
                print("SUBSCRIPTION TRIGGERED")
                if let result = result {
                    print("RESULT")
                    print(result.data!.watchState!.state)
                } else if let error = error {
                    print("ERROR")
                    print(error.localizedDescription)
                }
            })
        } catch {
            print("Error starting subscription.")
        }

我可以根据需要提供其他详细信息！我的“ SUBSCRIPTION TRIGGERED”打印声明从不打印，即使我通过AppSync控制台发送了成功更改“状态”数据的Mutation。