如何从AppDelegate调用ViewController.m中的函数？

Question

- (void)applicationDidBecomeActive:(UIApplication *)application {
    UIViewController* root = _window.rootViewController;
    UINavigationController* navController = (UINavigationController*)root;


    UIViewController  mycontroller = (UIViewController )[[navController viewControllers] objectAtIndex:0];
    [mycontroller serverSync];
}

我使用此代码，但出现错误：

ld：架构x86_64 clang的110个重复符号：错误：链接器命令失败，退出代码为1（使用-v查看调用）

怎么修？

Answer 1

110 duplicate symbols表示，与尝试从应用程序委托中调用视图控制器的serverSync函数相比，您遇到的问题要serverSync 。

与其在您的应用程序委托中进行serverSync将其放入视图控制器的viewDidLoad方法中。

更好的是，创建一个执行serverSync的单例对象，并且视图控制器可以从那里访问和使用服务器数据。

Answer 2

您可以为此使用NSNotificationCenter。 这是例子。

在您的AppDelgate.m中

- (void)applicationDidBecomeActive:(UIApplication *)application {
    [[NSNotificationCenter defaultCenter]
     postNotificationName:@"iOStpoint.wordpress.com"
     object:self];
    // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
}

在您的ViewController.m中

- (void)viewDidLoad {
    [super viewDidLoad];
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(receiveTestNotification:)
                                                 name:@"iOStpoint.wordpress.com"
                                               object:nil];
    // Do any additional setup after loading the view, typically from a nib.
}

- (void) receiveTestNotification:(NSNotification *) notification
{

    if ([[notification name] isEqualToString:@"iOStpoint.wordpress.com"])
        NSLog (@"Successfully received the test notification!");
}