发生错误时调用 completionHandler

Question

我正在尝试将布尔值传递给我的完成处理程序。当应用程序运行时，将 bool 传递给我的完成处理程序的结果决定了我显示的警报。如果我在我的错误检查中调用它，应用程序 crashes/locks 启动。如果我在其他任何地方调用它，一切都会按预期进行吗？我迷路了，找不到这个问题的答案。请帮忙。

class func TestConnection(_ urlBase: String, usingCommand command: String, completionHandler: @escaping (Bool) -> Void) {
        let urlString = urlBase + "/" + command
        var IsValidConnection = false
        guard let url = URL(string: urlString) else {
            completionHandler(IsValidConnection)
            return
        }

        URLSession.shared.dataTask(with: url) { (data, response, error) in      
            //App blows up when running this block of code.
            //Doesn't return. App crashes/locks up
            guard error == nil else {
                completionHandler(false)
                return
            }
            //App works as expected when running code below
            guard let _: HTTPURLResponse = response as? HTTPURLResponse else {
                completionHandler(false)
                return
            }

            let serverResponse = response as! HTTPURLResponse

            if serverResponse.statusCode == 200 {
                IsValidConnection = true
            }

            completionHandler(IsValidConnection)

        }.resume()
    }

Answer 1

问题是 URLSession.shared.dataTask 有自己的 completionHandler，名为 completionHandler。只需将您的处理程序重命名为 testConnectionCompletionHandler:

class func TestConnection(_ urlBase: String, usingCommand command: String, testConnectionCompletionHandler: @escaping (Bool) -> Void) {
    let urlString = urlBase + "/" + command
    var IsValidConnection = false
    guard let url = URL(string: urlString) else {
        testConnectionCompletionHandler(IsValidConnection)
        return
    }

    URLSession.shared.dataTask(with: url) { (data, response, error) in      
        //App blows up when running this block of code.
        //Doesn't return. App crashes/locks up
        guard error == nil else {
            testConnectionCompletionHandler(false)
            return
        }
        //App works as expected when running code below
        guard let _: HTTPURLResponse = response as? HTTPURLResponse else {
            testConnectionCompletionHandler(false)
            return
        }

        let serverResponse = response as! HTTPURLResponse

        if serverResponse.statusCode == 200 {
            IsValidConnection = true
        }

        testConnectionCompletionHandler(IsValidConnection)

    }.resume()
}

更多信息：https://developer.apple.com/documentation/foundation/urlsession/1407613-datatask

发生错误时调用 completionHandler

Calling a completionHandler when an error occurs

completionhandler

swift