如何在 swift 完成 api 调用后运行函数

Question

我希望我的函数 openDoor 返回 true，如果 API 调用给了我们 doorStatus“OPENED” 但是，我遇到了一个问题，这个函数在 API 调用之前返回，每次都返回 false，因为它有如此初始化。 我的问题是如何首先发出 api 请求，以便我可以根据该 API 调用分配 doorStatusL true 或 false 以在最后返回它？

                func openDoor(requesto: URLRequest) ->Bool {
                 var doorstatusL = false;


                func sendRequest() -> Bool {
                NSURLConnection.sendAsynchronousRequest(requesto, queue: OperationQueue.main) {(response, data, error) in

                    guard let data = data else {
                        return
                    }
                    print(String(data: data, encoding: .utf8)!)
                    do {

                        let json = try JSONDecoder().decode([WelcomeElement].self, from: data )
                        //try JSONSerialization.jsonObject(with: data!, options: [])
                        print(json[0].doorstatus)
                        if(json[0].doorstatus == "OPENED"){
                            doorstatusL = true;
                            print(doorstatusL)
                            print("assigned TRUE")
                        }
                    } catch {
                        print("Status Error during JSON serialization: \(error.localizedDescription)")
                    }
                    }
                    return true
                }
                if(sendRequest()==true){
                    print(doorstatusL)
                    print("=======+++++++")
                    return doorstatusL
                } else {
                    print("returned false at the end")
                    return false
                }  
               return true;
            }

终端的输出是

false
=======+++++++
[{"message":"OPEN, ENTER ","doorstatus":"OPENED"}] 
OPENED
true
assigned TRUE

谢谢

解决了

                        func sendRequest(requesto: URLRequest, success:Bool, completionHandler: @escaping (Bool)->Void) {
                        var doorStatusL = false

                        NSURLConnection.sendAsynchronousRequest(requesto, queue: OperationQueue.main) { (response, data, error) in
                            guard let data = data else { return }

                            do {
                                let json = try JSONDecoder().decode([WelcomeElement].self, from: data )

                                if(json[0].doorstatus == "OPENED") {
                                    doorStatusL = true
                                    completionHandler(doorStatusL)
                                }
                            } catch {
                                print("Status Error during JSON serialization: \(error.localizedDescription)")
                            }
                        }
                    }

                    let completionhandler:(Bool)->Void = { (success) in
                        if success {
                                sendNotifications()
                        }
                    }

                    sendRequest(requesto: request2, success: true, completionHandler: completionhandler)

Answer 1

func openDoor(requesto: URLRequest,completionHandler:@escaping (Bool) -> ()) {
    func sendRequest() -> Bool {
            NSURLConnection.sendAsynchronousRequest(requesto, queue: OperationQueue.main) {(response, data, error) in

                guard let data = data else {
                    return
                }
                print(String(data: data, encoding: .utf8)!)
                do {

                    let json = try JSONDecoder().decode([WelcomeElement].self, from: data )
                    //try JSONSerialization.jsonObject(with: data!, options: [])
                    print(json[0].doorstatus)
                    if(json[0].doorstatus == "OPENED"){
                        doorstatusL = true;
                        print(doorstatusL)
                        print("assigned TRUE")
                    }
                } catch {
                    print("Status Error during JSON serialization: \(error.localizedDescription)")
                }
                }
                completionHandler(true)
            }
            if(sendRequest()==true){
                print(doorstatusL)
                print("=======+++++++")
                completionHandler(doorstatusL) 
            } else {
                print("returned false at the end")
                completionHandler(false)
            }  
    })
}

用法：

openDoor() { requesto: urlHere,success in
   print(success)
}

转义闭包：转义闭包是在传递给它的函数返回后调用的闭包。 换句话说，它比传递给它的函数寿命更长。

非转义闭包：在它被传入的函数内调用的闭包，即在它返回之前。

你可以在这个问题中阅读更多关于它的信息： Swift @escaping and Completion Handler

Answer 2

将完成处理程序添加到 api 调用方法

func sendRequest(completion:@escaping (_ response:Bool) -> Void){
   completion(true)
}

然后你可以在完成时调用一个函数

sendRequest(completion: {_ in
    yourFunction()
})