如何從AppDelegate調用ViewController.m中的函數？

Question

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


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

我使用此代碼，但出現錯誤：

ld：架構x86_64 clang的110個重復符號：錯誤：鏈接器命令失敗，退出代碼為1（使用-v查看調用）

怎么修？

Answer 1

110 duplicate symbols表示，與嘗試從應用程序委托中調用視圖控制器的serverSync函數相比，您遇到的問題要serverSync 。

與其在您的應用程序委托中進行serverSync將其放入視圖控制器的viewDidLoad方法中。

更好的是，創建一個執行serverSync的單例對象，並且視圖控制器可以從那里訪問和使用服務器數據。

Answer 2

您可以為此使用NSNotificationCenter。 這是例子。

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!");
}