當我嘗試在文本框中輸入時，出現EXC_BAD_ACCESS（代碼= 2地址= 0x0）錯誤

Question

我是一名從遠處國家學習英語和Objective-C的學生。

下面的代碼是測試代碼，當我在文本字段中鍵入內容時。然後立即在命令行上打印一個字符。

但是當我觸摸正在運行的應用程序的文本。發生模糊的錯誤。

#import "SimpleViewController.h" 
#import "SimpleTextFieldDelegate.h" 

@interface SimpleViewController() 

@end 

@implementation SimpleViewController 

@synthesize field; 
@synthesize label; 

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil 
{ 
    // Nothing special in here. 
} 

- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 

    NSLog(@"Do this will be printed on command line?"); 
    [self.field setDelegate: [[SimpleTextFieldDelegate alloc] init]]; 
} 

@end

這是SimpleViewController類實現代碼。

int main(int argc, char * argv[]) 
{ 
    @autoreleasepool { 
     return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class])); 
                <- error caused at here. 
    } 
} 

爲什麼我得到這個錯誤？我無法猜出任何猜測。

Answer 1

#import "SimpleViewController.h" 
#import "SimpleTextFieldDelegate.h" 

@interface SimpleViewController() 
@property SimpleTextFieldDelegate MySimpleTextFieldDelegate; 
@end 

@implementation SimpleViewController 

@synthesize field; 
@synthesize label; 
@synthesize MySimpleTextFieldDelegate; 

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil 
{ 

//這裏沒什麼特別的。 }

- (void)viewDidLoad 
{ 
[super viewDidLoad]; 

MySimpleTextFieldDelegate = [[SimpleTextFieldDelegate alloc] init]; 

NSLog(@"Do this will be printed on command line?"); 
[self.field setDelegate:MySimpleTextFieldDelegate]; 
}