iOS 后台获取和完成 block

Question

我正在尝试定义这个方法

- (void)backgroundFetchWithCompletion:(void(^)(UIBackgroundFetchResult))completionHandler;

但是我在 UIBackgroundFetchResult 上收到一个错误，说只允许没有类型的参数列表，我正在学习本教程和这个 tutorial这就是他们定义方法的方式。

Answer 1

最后执行一些操作后，您必须调用列表中的一个。

objective-C

1. completionHandler(UIBackgroundFetchResultNewData);
2. completionHandler(UIBackgroundFetchResultFailed);
3. completionHandler(UIBackgroundFetchResultNoData);

swift

1. completionHandler(.NewData)
2. completionHandler(.Failed)
3. completionHandler(.NoData)

完整示例:

objective-C

- (void)application:(UIApplication *)application performFetchWithCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler
{
  NSLog(@"performFetchWithCompletionHandler");
  //Perform some operation
  completionHandler(UIBackgroundFetchResultNewData);
}

swift

func application(application: UIApplication, performFetchWithCompletionHandler completionHandler: (UIBackgroundFetchResult) -> Void) {
  println("performFetchWithCompletionHandler")
  //Perform some operation
  completionHandler(.NewData)
}