Swift 用于 JSON 请求的 AlamoFire 异步完成处理程序

这是一个非常好的问题.你的方法完全正确.然而，Alamofire实际上可以帮助您进一步简化这一过程.

您的示例代码分派队列细分

在示例代码中，您正在以下调度队列之间 skip :

1. NSURLSession调度队列
2. 用于验证和序列化程序处理的TaskDelegate调度队列
3. 用于调用完成处理程序的主调度队列
4. 用于JSON处理的高优先级队列
5. 用于更新用户界面的主调度队列(如有必要)

正如你所见，你到处都是.让我们来看看另一种利用Alamofire内部强大功能的方法.

Alamofire响应调度队列

Alamofire在其自身的低级别处理中内置了一种最佳方法.最终被所有自定义响应序列化程序调用的单个response方法支持自定义调度队列(如果您 Select 使用它).

虽然GCD在调度队列之间的跳转非常出色，但您希望避免跳转到繁忙的队列(例如主线程).通过消除在异步处理中间的主线程的跳转，可以极大地加快速度.下面的示例演示了如何直接使用Alamofire逻辑实现这一点.

阿拉莫菲尔1号.十、

let queue = dispatch_queue_create("com.cnoon.manager-response-queue", DISPATCH_QUEUE_CONCURRENT)

let request = Alamofire.request(.GET, "http://httpbin.org/get", parameters: ["foo": "bar"])
request.response(
    queue: queue,
    serializer: Request.JSONResponseSerializer(options: .AllowFragments),
    completionHandler: { _, _, JSON, _ in

        // You are now running on the concurrent `queue` you created earlier.
        println("Parsing JSON on thread: \(NSThread.currentThread()) is main thread: \(NSThread.isMainThread())")

        // Validate your JSON response and convert into model objects if necessary
        println(JSON)

        // To update anything on the main thread, just jump back on like so.
        dispatch_async(dispatch_get_main_queue()) {
            println("Am I back on the main thread: \(NSThread.isMainThread())")
        }
    }
)

阿拉莫菲尔3号.x(Swift 2.2和2.3)

let queue = dispatch_queue_create("com.cnoon.manager-response-queue", DISPATCH_QUEUE_CONCURRENT)

let request = Alamofire.request(.GET, "http://httpbin.org/get", parameters: ["foo": "bar"])
request.response(
    queue: queue,
    responseSerializer: Request.JSONResponseSerializer(options: .AllowFragments),
    completionHandler: { response in
        // You are now running on the concurrent `queue` you created earlier.
        print("Parsing JSON on thread: \(NSThread.currentThread()) is main thread: \(NSThread.isMainThread())")

        // Validate your JSON response and convert into model objects if necessary
        print(response.result.value)

        // To update anything on the main thread, just jump back on like so.
        dispatch_async(dispatch_get_main_queue()) {
            print("Am I back on the main thread: \(NSThread.isMainThread())")
        }
    }
)

阿拉莫菲尔4号.x(Swift 3)

let queue = DispatchQueue(label: "com.cnoon.response-queue", qos: .utility, attributes: [.concurrent])

Alamofire.request("http://httpbin.org/get", parameters: ["foo": "bar"])
    .response(
        queue: queue,
        responseSerializer: DataRequest.jsonResponseSerializer(),
        completionHandler: { response in
            // You are now running on the concurrent `queue` you created earlier.
            print("Parsing JSON on thread: \(Thread.current) is main thread: \(Thread.isMainThread)")

            // Validate your JSON response and convert into model objects if necessary
            print(response.result.value)

            // To update anything on the main thread, just jump back on like so.
            DispatchQueue.main.async {
                print("Am I back on the main thread: \(Thread.isMainThread)")
            }
        }
    )

阿拉莫菲尔调度队列故障

下面是这种方法涉及的不同调度队列的分类.

1. NSURLSession调度队列
2. 用于验证和序列化程序处理的TaskDelegate调度队列
3. 用于JSON处理的自定义管理器并发调度队列
4. 用于更新用户界面的主调度队列(如有必要)

总结

通过消除返回主调度队列的第一跳，您消除了一个潜在的瓶颈，并且使整个请求和处理变得异步.令人惊叹的

尽管如此，我还是要强调，熟悉Alamofire的工作原理是多么重要.你永远不知道什么时候你能找到真正能帮助你改进自己代码的东西.