从回调函数中获取值swift

Question

问题我想从我的ApiToken函数返回值，以便我可以在另一个函数中使用它。由于某些原因，我无法从这个函数获取值，它不会返回任何东西。我怎么能从我的ApiToken函数返回值，并在另一个函数中使用它。

这是我GetApiToken类的ApiToken功能

class GetApiToken { 



    public func ApiToken(link: String, completionBlock: @escaping (String) -> Void) -> Void 
    { 
     let url = URL(string: link)! 
     let jsonDict = ["username": "snow", "password": "ssssssssss"] 
     let jsonData = try! JSONSerialization.data(withJSONObject: jsonDict, options: []) 

     var request = URLRequest(url: url) 
     request.httpMethod = "post" 
     request.setValue("application/json", forHTTPHeaderField: "Content-Type") 
     request.httpBody = jsonData 

     let task = URLSession.shared.dataTask(with: request) { (data, response, error) in 
      if let error = error { 
       print("error:", error) 
       return 
      } 

      do { 
       guard let data = data else { return } 

       guard let json = try JSONSerialization.jsonObject(with: data, options: []) as? [String: AnyObject] else { return } 

       //self.token = json["access_token"] as? String ?? "x" 
       completionBlock((json["access_token"] as? String)!) 



      } catch { 
       print("error:", error) 
      } 
     } 

     task.resume() 
    } 
} 

这里就是我试图获得价值

func getData(_ link:String) 
    { 
     let url = URL(string: link)! 
     var request = URLRequest(url: url, cachePolicy: .reloadIgnoringCacheData, timeoutInterval: 20) 
     request.httpMethod = "GET" 
     var output = "" 
     GetApiToken().ApiToken(link: "http://localhost:5000/auth", completionBlock: { str in 
      output = str 

     }) 
     request.addValue("JWT \(output)", forHTTPHeaderField: "Authorization") 
     request.setValue("application/json", forHTTPHeaderField: "Content-Type") .......... 

Answer 1

这是一个异步调用，所以你需要把一切会一旦在完成回调中检索到数据，就会发生这种情况

func getData(_ link:String) 
{ 
    let url = URL(string: link)! 
    var request = URLRequest(url: url, 
          cachePolicy: .reloadIgnoringCacheData, 
          timeoutInterval: 20) 
    request.httpMethod = "GET" 
    GetApiToken().ApiToken(link: "http://localhost:5000/auth", 
          completionBlock: 
          { output in 
          request.addValue("JWT \(output)", forHTTPHeaderField: "Authorization") 
          request.setValue("application/json", forHTTPHeaderField: "Content-Type") 
          ....... 
          })