使用UIButton转换UIViews时遇到困难

Question

我是一个非常没经验的开发人员，遇到了一个应该很容易的问题，但是在Apple的开发人员指南上阅读了数小时后，本网站上的许多不同问题仍然难以理解。

我想要做的就是通过UIButton从我的根视图控制器转换到我的下一个视图控制器。

这里是appdelegate.h：

#import <UIKit/UIKit.h> 

@class MainViewController; 

@interface MDAppDelegate : NSObject <UIApplicationDelegate> { 

    UIWindow *window; 
    UINavigationController *navigationController; 
} 

@property (nonatomic, retain) IBOutlet UIWindow *window; 
@property (nonatomic, retain) IBOutlet UINavigationController *navigationController; 

@end 

从Appdelegate.m重要的东西：

#import "MDAppDelegate.h" 
#import "MainViewController.h" 

@implementation MDAppDelegate 


@synthesize window, navigationController; 

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions (NSDictionary *)launchOptions 

{

// Override point for customization after application launch. 
    [window addSubview:navigationController.view]; 
    [self.window makeKeyAndVisible]; 
    return YES; 
} 

MainViewController.h：

#import <UIKit/UIKit.h> 


@interface MainViewController : UIViewController { 

UIButton *cityButton; 

} 

@property (nonatomic, retain) IBOutlet UIButton *cityButton; 

- (IBAction)chooseCityAction:(id)sender; 

@end 

最后，MainViewController.m：

#import "MainViewController.h" 
#import "DailyDealViewController.h" 


@implementation MainViewController 
@synthesize cityButton; 

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil 
{ 
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]; 
    if (self) { 

    } 

return self; 

} 

- (void)dealloc 
{ 
    [cityButton release]; 

    [super dealloc]; 
} 

- (void)didReceiveMemoryWarning 
{ 
    // Releases the view if it doesn't have a superview. 
    [super didReceiveMemoryWarning]; 

    // Release any cached data, images, etc that aren't in use. 
} 

#pragma mark - View lifecycle 

- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 
    // Do any additional setup after loading the view from its nib. 

    UIBarButtonItem *temporaryBarButtonItem = [[UIBarButtonItem alloc] init]; 
    temporaryBarButtonItem.title = @"Back"; 
self.navigationItem.backBarButtonItem = temporaryBarButtonItem; 
[temporaryBarButtonItem release]; 


} 

- (void)viewDidUnload 
{ 
    [self setCityButton:nil]; 
    [super viewDidUnload]; 
    // Release any retained subviews of the main view. 
    // e.g. self.myOutlet = nil; 
} 

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation 
{ 
    // Return YES for supported orientations 
    return (interfaceOrientation == UIInterfaceOrientationPortrait); 
} 

- (IBAction)chooseCityAction:(id)sender { 

    DailyDealViewController *dailyDealViewController = [[DailyDealViewController alloc]initWithNibName:@"DailyDealViewController" bundle:nil]; 

    [dailyDealViewController release]; 

    [self.navigationController pushViewController:dailyDealViewController animated:YES]; 

} 
@end 

以下是错误：

2011-10-03 21:56:14.258 MD[4235:207] *** Terminating app due to uncaught exception 
'NSUnknownKeyException', reason: '[<UIViewController 0x4b434c0> 
setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key 
cityButton.' 

我很想知道我错过了什么。

Answer 1

在推送之前，您已经发布了dailyDealViewController。将发布声明移至pushViewController声明之后。