Question

我目前正在尝试使用WWDC期间介绍的有关高级NSOperations的概念。我想将使用不同class DownloadOperation : GroupOperation { let requestContext:RequestContext init(context:RequestContext, apiCall:API){ requestContext = context super.init(operations: []) name = "Generic Download" guard let URL = apiCall.URLRequest else { finish() return } let dataTask = NSURLSession.sharedSession().dataTaskWithURL(URL) { data, response, error in self.downloadFinished(data, response: response as? NSHTTPURLResponse, error: error) } let downloadTask = URLSessionTaskOperation(task: dataTask) let reachabilityCondition = ReachabilityCondition(host: URL) let networkObserver = NetworkObserver() downloadTask.addCondition(reachabilityCondition) downloadTask.addObserver(networkObserver) addOperation(downloadTask) } private func downloadFinished(data:NSData?, response:NSHTTPURLResponse?, error:NSError?){ if let data = data { requestContext.data = data requestContext.httpResponse = response } else { finishWithError(error) } } }子类（以及扩展任何类型的链接操作）的请求分开。

我使用上下文类在流程中涉及的所有操作之间共享数据（参见：Passing Data Between Two NSOperations）

class JSONUnmarshallOperation: Operation {

        let context:RequestContext

        init(context c:RequestContext){
            self.context = c

            super.init()

            name = "JSON Parsing"
        }

        final override func execute() {
            guard let data = context.data else { finish(); return }

            defer {
                context.data = nil
            }

            do {
                context.JSON = try NSJSONSerialization.JSONObjectWithData(data, options: [])
                finish()
            } catch let error as NSError {
                finishWithError(error)
            }

        }
    }

每个子类在初始化期间获得对上下文的引用。

下载示例：

GroupOperation

JSON解析示例：

 class SomeOperation: GroupOperation {

    let downloadOperation:DownloadOperation
    let unmarshalOperation:JSONUnmarshallOperation

    init (completionHandler:<* Some Type *>) {

        let blockOperation = NSBlockOperation {

            //Use the callback here and access self
        }


        super.init(operations:[downloadOperation, unmarshalOperation, blockOperation])
    }
}

我希望能够创建依赖于这两个操作的self并定义完成回调。我想有这样的事情：

super.init

这里的问题是，在致电GroupOperation

之前，我会访问

sudo npm update npm -g

是否有一种简单而优雅的方式来添加通用完成处理程序添加{{1}}子类的结尾？

Answer 1

简单的答案是，在您致电blockOperation之后才构建super.init：

init (completionHandler:<* Some Type *>) {
    let downloadOperation = ...
    let unmarshallOperation = ...
    unmarshallOperation.addDependency(downloadOperation)

    super.init(operations:[downloadOperation, unmarshallOperation, blockOperation])

    let blockOperation = NSBlockOperation {
        //Use the callback here and access self
    }
    blockOperation.addDependency(unmarshallOperation)
    addOperation(blockOperation)
}

高级NSOperations，GroupOperation的回调

1 个答案: