iPhone代表問題

我有2個意見。 firstView和secondView。 firstView需要secondView的收藏夾陣列，所以我嘗試調用協議中定義的getFavourites方法。然而，這返回null，這對我來說似乎很陌生，因爲一切都合情合理。iPhone代表問題

這裏是firstViewController.h：

#import <UIKit/UIKit.h> 
#import "Drink.h" 

@protocol firstViewControllerDelegate; 

@interface FirstViewController : UIViewController 
{ 
    id <firstViewControllerDelegate> delegate; 
    NSMutableArray *labels; 

    UIButton *button1; 
    UIButton *button2; 
    UIButton *button3; 
    UIButton *button4; 
} 

- (IBAction) buttonClick: (id) sender; 

@property (nonatomic, assign) id <firstViewControllerDelegate> delegate; 
@property (nonatomic, retain) IBOutlet UIButton *button1; 
@property (nonatomic, retain) IBOutlet UIButton *button2; 
@property (nonatomic, retain) IBOutlet UIButton *button3; 
@property (nonatomic, retain) IBOutlet UIButton *button4; 

@end 

@protocol firstViewControllerDelegate 
- (NSMutableArray *) getFavourites; 
- (void) setFavourites: NSMutableArray; 
@end

firstViewController.m

@synthesize delegate; 

....... 

- (void) viewWillAppear:(BOOL)animated 
{ 
    NSMutableArray *favourites = [delegate getFavourites]; // favourites is empty after this line 
    [button1 setTitle:[[favourites objectAtIndex:1] name] forState:UIControlStateNormal]; 
    NSLog(@"VIEW APPEARED. BUTTON TITLE IS: %@", button1.currentTitle); 
}

SecondViewController.h

#import <UIKit/UIKit.h> 
#import "FirstViewController.h" 

@interface SecondViewController: UIViewController <UITableViewDelegate, UITableViewDataSource, UITextFieldDelegate, firstViewControllerDelegate> 
{ 
     NSMutableArray *favourites; 
     NSMutableArray *drinks; 
} 

@property (nonatomic, retain) NSMutableArray *drinks; 
@property (nonatomic, retain, getter = getFavourites) NSMutableArray *favourites; 

- (void) addDrink: (NSString *) name; 

@end

有誰知道這是爲什麼不工作的任何想法？

來源

2011-09-19 JheeBz

你檢查委託當時getFavorites分配被稱爲？ – Fuggly

你是什麼意思？我需要將其分配給什麼以及如何分配？ – JheeBz

用'@property（nonatomic，retain）IBOutlet SecondViewController * delegate'替換委託屬性，轉到xib，放下視圖控制器圖標，將其設置爲SecondController並將其鏈接到屬性。另一種方法是在viewDidLoad中實例化控制器。我認爲你不太理解委託和控制器的概念，但這並不妨礙你的工作。 – Jano

你確定你正在設置FirstViewController的委託屬性嗎？即：

FirstViewController *firstController = // Instantiate the controller; 
firstController.delegate = secondController; 
[self.navigationController pushViewController:firstController animated:YES];

secondController應該實例化之前存在的，否則你設置一個nil值

來源

2014-04-29 20:06:44 HighFlyingFantasy

iPhone代表問題

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