我如何将数据传递给swift4中的变量? [英] How i can pass the data to a variable in swift4?

问题描述

我需要在另一个viewcontroller中使用输出数据，但是我不能使用，该字符串仅返回一个空字符串:

I need to use the output data in another viewcontroller but I can't use, the string only returns an empty string :

func callApi(postString: String) -> (String) {
    var outputdata = String()
    var req = LogIn(postString: postString)
    let task = URLSession.shared.dataTask(with: req) { (data, response, error) in
        if let data = data{
            outputdata = String(data: data, encoding: String.Encoding.utf8)!
            //print(outputdata)


        }
    }

    print(outputdata)
    return (outputdata)
}

推荐答案

您可以尝试此操作，因为该过程是异步的

You can try this as the process is asynchronous

func callApi(_ postString: String,completion:@escaping:(_ res:String?) -> Void ) {
     var req = LogIn(postString: postString)
    URLSession.shared.dataTask(with: req) { (data, response, error) in
        if let data = data{
            completion(String(data: data, encoding: String.Encoding.utf8))     
        }
        else {
            completion(nil)
        }
    }.resume()
 }

致电

callApi("SendedValue") {  res in
  print(res)
}

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