如何同步闭包？

Question

如何同步闭包？

我有这个代码:

    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,而不是当所有请求都将结束时我需要调用完成？()当所有请求都将结束时.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a的版本DispatchGroup.

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?()
    }
}