迅速3完成处理程序以返回字符串 [英] swift 3 completion handler to return string

问题描述

我是新手，从函数获取字符串时遇到问题，我正在尝试使用完成处理程序，但是出了点问题，您能帮我吗?

I am new at swift and got problem with getting string from function, I am trying to use completion handler, but something is wrong, could you help me?

将[String:String]添加到func之后，我无法获得响应，我想获取响应并进行打印.错误:无法将类型()的返回表达式转换为返回类型[String:String]

After adding [String : String] to func, I cant get rezult, I want to get response and print it. Error: Cannot convert return expresion of type () to return type [String : String]

请求:

public func login(userName: String, password: String) -> [String : String]{

let loginrequest = JsonRequests.loginRequest(userName: userName, password: password)
return makeWebServiceCall(urlAddress: URL, requestMethod: .post, params: loginrequest, completion: { (JSON : Any) in

   print("\(JSON)")

})

}


private func makeWebServiceCall (urlAddress: String, requestMethod: HTTPMethod, params:[String:Any], completion: @escaping (_ JSON : Any) -> ()) {


    Alamofire.request(urlAddress, method: requestMethod, parameters: params, encoding: JSONEncoding.default).responseJSON { response in

        switch response.result {
        case .success:
            if let jsonData = response.result.value {
                completion(jsonData)
            }
        case .failure(let error):
            if let data = response.data {
                let json = String(data: data, encoding: String.Encoding.utf8)
                print("Failure Response: \(json)")

            }

呼叫功能:

let retur = Json()
    let rezultatas = retur.login(userName: "root", password: "admin01")

    print(rezultatas)

错误: 在此处输入图片描述

推荐答案

欢迎使用Swift :)

Welcome to Swift :)

您正在将同步和异步代码混合在一起.

You are mixing synchronous and asynchronous code together.

当您呼叫login时，您希望它立即返回类型为[String : String]的答案.

When you call login you expect it to return an answer straight away of type [String : String].

但是，在您的login方法中，您进行了无法立即返回的网络调用...这就是为什么对Alamofire.request的调用将完成块作为参数的原因.

But in your login method you then do a network call which can not return straight away...which is why the call to Alamofire.requesttakes a completion block as a parameter.

所以...您需要更改您的login方法，以便:

So...you need to change your login method so it:

1. 不立即返回任何内容(不能这样做...登录要求我们进行网络通话记住)
2. 登录成功后，将调用一个完成块.

可以这样做:

public func login(userName: String, password: String, loginCompletion: @escaping ([String : String]) -> ())

这里我们有一个函数，该函数采用类型String的userName，类型String的password和类型function的loginCompletion，该函数再次使用[String : String]字典作为参数.请注意，该方法不返回任何内容.

Here we have a function that takes a userName of type String, a password of type String and a loginCompletion of type function that again takes a [String : String] dictionary as a parameter. Notice that the method does not return anything.

现在，您几乎可以像以前一样拨打makeWebServiceCall了:

Now you can call your makeWebServiceCall almost as before:

let loginrequest = JsonRequests.loginRequest(userName: userName, password: password)
makeWebServiceCall(urlAddress: URL, requestMethod: .post, params: loginrequest, completion: { (JSON : Any) in
   //Now we are ready, the login call has returned some data to you. 

   //You have an attribute named JSON of type Any, which you need to convert to [String : String], and then you can call loginCompletion with that, like so:
   loginCompletion(yourConvertedDictionaryHere)
})

这是完整的新login方法:

public func login(userName: String, password: String, loginCompletion: @escaping ([String : String]) -> ()) {
    let loginrequest = JsonRequests.loginRequest(userName: userName, password: password)
    makeWebServiceCall(urlAddress: URL, requestMethod: .post, params: loginrequest, completion: { (JSON : Any) in
       //Now we are ready, the login call has returned some data to you. 

       //You have an attribute named JSON of type Any, which you need to convert to [String : String], and then you can call loginCompletion with that, like so:
       loginCompletion(yourConvertedDictionaryHere)
    })
}

然后像这样调用login方法:

retur.login(userName: "root", password: "admin01") { stringDictionary: [String : String] in
    //here you have your stringDictionary which you can use as pleased
}

希望对您有帮助.

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