Swift：AppDelegate中的AppStart中的Network-Request - ViewController中的CompletionHandler？

Question

我的应用程序基于带有4个ViewControllers的TabBarController。所有4个都依赖于相同的数据。这就是为什么我想要在AppDelegate的App start中加载数据的原因。

但是，ViewController如何知道请求已完成？例如，如果发生错误（例如没有互联网连接），我如何将这个错误传递给这4个ViewController中的任何一个来显示警报？

Answer 1

使用通知中心来实现（SWIFT 3码）：

extension Notification.Name { 
    static var RequestCompleted = Notification.Name(rawValue: "MyRequestIsCompleted") 
    static var RequestError = Notification.Name(rawValue: "MyRequestError") 
} 

class DataRequest { 

    func request() { 

     // if there is error: 
     let error = NSError(domain: "Error Sample", code: 0, userInfo: nil) 
     NotificationCenter.default.post(name: .RequestError, object: error) 

     // if the request is completed 
     let data = "your data is here" 
     NotificationCenter.default.post(name: .RequestCompleted, object: data) 

    } 

} 

class ViewController: UIViewController { 

    override func viewDidLoad() { 
     super.viewDidLoad() 

     NotificationCenter.default.addObserver(self, selector: #selector(requestCompleted(_:)), name: .RequestCompleted, object: nil) 
     NotificationCenter.default.addObserver(self, selector: #selector(requestError(_:)), name: .RequestError, object: nil) 

    } 

    deinit { 
     NotificationCenter.default.removeObserver(self) 
    } 

    func requestCompleted(_ notification: Notification) { 
     if let obj = notification.object { 
      print(obj) 
     } 
    } 

    func requestError(_ notification: Notification) { 
     if let obj = notification.object { 
      print(obj) 
     } 
    } 

}