Question

如何同步闭包？

我有这段代码：

    private func getWeather(parameters: [String : Any],  failure: ((String) -> Void)? = nil ,completion: (() -> Void)? = nil) {

        for _ in 0...10 {

            RequestManager.sharedInstance.request(url: baseURL, parameters: parameters, completion:  { (result) in
                if JSON.parse(result)["name"].string == nil {
                    failure?("Something went wrong. Please, try again later")
                } else {
                    let weatherModel: WeatherModel = WeatherModel(json: JSON.parse(result))
                }
            })
        }
        completion?()

    }

在我的代码中，完成？（）将调用，而不是所有请求都将结束当所有请求都结束时，我需要调用完成？（）。我可以这样做吗？

Answer 1

由于当前接受的答案不正确，因此这是一个正确使用DispatchGroup的版本。

private func getWeather(parameters: [String : Any],  failure: ((String) -> Void)? = nil ,completion: (() -> Void)? = nil) {
    let dispatchGroup = DispatchGroup()
    for _ in 0...10 {
        dispatchGroup.enter()
        RequestManager.sharedInstance.request(url: baseURL, parameters: parameters) { result in
            if JSON.parse(result)["name"].string == nil {
                failure?("Something went wrong. Please, try again later")
            } else {
                let weatherModel: WeatherModel = WeatherModel(json: JSON.parse(result))
            }
            dispatchGroup.leave()
        }
    }

    dispatchGroup.notify(queue: DispatchQueue.main) {
        completion?()
    }
}

Answer 2

一种简单的方法就是计算已完成的电话。

private func getWeather(parameters: [String : Any],  failure: ((String) -> Void)? = nil ,completion: (() -> Void)? = nil) {
    let numCalls = 11;
    var completedCalls = 0;

    for _ in 0..<numCalls {

        RequestManager.sharedInstance.request(url: baseURL, parameters: parameters, completion:  { (result) in
            if JSON.parse(result)["name"].string == nil {
                failure?("Something went wrong. Please, try again later")
            } else {
                let weatherModel: WeatherModel = WeatherModel(json: JSON.parse(result))
            }
            completedCalls += 1
            if completedCalls == numCalls {
                completion?()
            }
        })
    }
}

每个请求结束时都会运行完成回调。使每个完成回调更新其封闭范围中的值允许您跟踪已结束的请求数。当您预期的所有请求都已结束时，请致电completion?()。

如何同步闭包？

2 个答案: