協議方法沒有被調用，顯示委託'nil'

我正在研究一個iPad應用程序，我遇到了委託問題......協議方法沒有被調用。我不確定我錯過了什麼，這裏是我的代碼。協議方法沒有被調用，顯示委託'nil'

@protocol pickerLabelProtocol <NSObject> 
- (void)selectedPickerData:(UILabel *)sender; 
@end 

@interface showPickerVC : UIViewController 
@property (nonatomic, strong) id <pickerLabelProtocol> delegate; 
@end 

@implementation showPickerVC 
- (void)viewWillDisappear:(BOOL)animated 
{ 
    [super viewWillDisappear:animated]; 
//i used breakpoint, the 'delegate' is always nil for some reason? 
    [self.delegate selectedPickerData:self.mainLabel]; 
} 

---------------------- 
@interface someViewController : UIViewController <pickerLabelProtocol> 
@property (nonatomic, strong) showPickerVC *showPicker; 
@end 

@implementation someViewController 

- (void)selectedPickerData:(UILabel *)sender 
{ 
//protocol method 
} 

- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 
    self.showPicker = [[showPickerVC alloc]init]; 
    self.showPicker.delegate = self; 
}

來源

2013-06-22 DevCali

究竟是你想要做什麼？你想要訪問什麼？ – Durgaprasad

「ShowPickerVC」是popOver，來自「someViewController」...「ShowPickerVC」有一個選擇器，用戶在選擇器中選擇數據，我希望選定的數據被傳遞給「someViewController」... – DevCali

我是不知道爲什麼，但這段代碼在iPhone中正常工作，但不與iPad可能是因爲popOver？ – DevCali

我不能有任何錯誤，從你的代碼，但我建議你要清楚，當你創建的showPickerVC對象添加它delegate自

諸如此類有關，

showPickerVC *obj = [[showPickerVC alloc] init]; 
obj.delegate = self; /// YOur protocol delegate 
. 
. 
[self presentModalViewController:obj animated:YES];

並且下面添加代碼

@implementation showPickerVC 

- (void)viewWillDisappear:(BOOL)animated 
{ 
    [super viewWillDisappear:animated]; 

    if([self.delegate respondsToSelector:@selector(selectedPickerData:)]) 
    { 
     [self.delegate selectedPickerData:self.mainLabel]; 
    } 

}

有關How to create/use of Protocol.的詳細信息

來源

2013-06-22 05:12:19 iPatel

感謝您的回覆......問題在於「委託」總是顯示爲零，這是爲什麼它不會調用該方法...是否與popOver有關？此代碼可以正常使用iPhone ... – DevCali

協議方法沒有被調用，顯示委託'nil'

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