没有已知的选择器实例方法 [英] No known instance method for selector
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问题描述
我正在使用最新的SDK, XCode 4.2 和 ARC 开发iOS 4应用程序.
I'm developing an iOS 4 application using latest SDK, XCode 4.2 and ARC.
我已将方法添加到appDelegate.h
#import <UIKit/UIKit.h>
@class ViewController;
@class SecondViewController;
@interface AppDelegate : UIResponder <UIApplicationDelegate>
{
UINavigationController* navController;
ViewController* viewController;
SecondViewController* secondViewController;
}
@property (strong, nonatomic) UIWindow *window;
- (void) showSecondViewController;
@end
它在appDelegate.m
#import "AppDelegate.h"
#import "ViewController.h"
#import "SecondViewController.h"
@implementation AppDelegate
@synthesize window = _window;
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
viewController = [[ViewController alloc] initWithNibName:@"ViewController" bundle:nil];
viewController.title = @"First";
navController = [[UINavigationController alloc] initWithRootViewController:viewController];
self.window.rootViewController = navController;
[self.window makeKeyAndVisible];
return YES;
}
- (void)applicationWillResignActive:(UIApplication *)application
{
...
}
- (void)applicationDidEnterBackground:(UIApplication *)application
{
...
}
- (void)applicationWillEnterForeground:(UIApplication *)application
{
...
}
- (void)applicationDidBecomeActive:(UIApplication *)application
{
...
}
- (void)applicationWillTerminate:(UIApplication *)application
{
...
}
- (void) showSecondViewController
{
secondViewController = [[SecondViewController alloc] initWithNibName:@"SecondViewController" bundle:nil];
secondViewController.title = @"Second";
[navController pushViewController:secondViewController animated:YES];
}
@end
但是,当我在ViewController.m中向该方法发送消息时
But, when I send a message to that method in ViewController.m
- (IBAction)goSecondClicked:(id)sender
{
[[[UIApplication sharedApplication] delegate] showSecondViewController];
}
我收到以下编译器错误:
I get the following compiler error:
自动参考计数问题 选择器'showSecondViewController'的未知实例方法
Automatic Reference Counting Issue No known instance method for selector 'showSecondViewController'
有任何线索吗?
推荐答案
您将需要强制转换为以下对象的委托对象:
You will need to cast the delegate object that you get as:
AppDelegate *appDelegate = (AppDelegate*)[[UIApplication sharedApplication] delegate];
然后在appDelegate
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