IOS，删除警告？

Question

我想删除这条线警告：

UIViewController * appController = [[[UIApplication sharedApplication] delegate]  viewController]; 

我得到这一行代码的警告是： “实例方法‘的viewController’未找到（返回类型默认为‘身份证’ ）

有人能帮助解释如何我可能会删除这个亏

非常感谢，

Answer 1

您需要投下您的应用程序委托：

UIViewController * appController = [(MyAppDelegate *)[[UIApplication sharedApplication] delegate] viewController]; 

Answer 2

添加投放到您的委托：？

UIViewController * appController = [(MyAppDelegate *)[[UIApplication sharedApplication] delegate] viewController]; 

Answer 3

我不知道你的...AppDelegate是如何被调用的，所以我在这里使用DemoAppDelegate。

UIViewController *appController = [(DemoAppDelegate *)[[UIApplication sharedApplication] delegate] viewController]; 

Answer 4

类型转换是嘈杂，可能是危险的。为了解决这个问题，我通常最终创建一个简单的类方法。假设类是一直打算用作应用程序的委托，你可以写这样的事情：

// MONApplicationDelegate.h 
@interface MONApplicationDelegate : NSObject <UIApplicationDelegate> 

// ... 

+ (MONApplicationDelegate *)sharedApplicationDelegate; 
- (UIViewController *)viewController; 

@end 

// MONApplicationDelegate.m 
@implementation MONApplicationDelegate 

// ... 

+ (MONApplicationDelegate *)sharedApplicationDelegate 
{ 
    id ret = [[UIApplication sharedApplication] delegate]; 
    if (nil == ret) { 
     assert(0 && "oops - app delegate has not been created yet"); 
     return nil; 
    } 
    if (![ret isKindOfClass:[MONApplicationDelegate class]]) { 
     assert(0 && "invalid class type for shared application delegate"); 
     return nil; 
    } 
    else { 
     return ret; 
    } 
} 

@end 

// in action 
UIViewController * appController = 
    [[MONApplicationDelegate sharedApplicationDelegate] viewController]; 

// which is shorter and safer to use, when compared to: 
UIViewController * appController = 
    [(MONApplicationDelegate*)[[UIApplication sharedApplication] delegate] viewController];