我正在尝试使用委托(delegate)将一个简单的字符串从一个 View Controller 发送到另一个 View Controller ，但我的委托(delegate)不起作用。我正在使用 Storyboard，不想使用 segue 来传递数据。这是我的简单代码

ViewControllerA.h

#import <UIKit/UIKit.h>

@class ViewControllerA;

@protocol viewControllerADelegate <NSObject>

-(void) addItem: (ViewControllerA *)controller data:(NSString *)item;

@end

@interface ViewControllerA : UIViewController{
 __weak id <viewControllerADelegate> delegate;
}
- (IBAction)buttonPressed:(id)sender;

@property (weak) id<viewControllerADelegate> delegate;
@end

ViewControllerA.m

#import "ViewControllerA.h"

@interface ViewControllerA ()

@end

@implementation ViewControllerA
@synthesize delegate;

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

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

}

- (void)viewDidUnload
{
[super viewDidUnload];
// Release any retained subviews of the main view.
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
 {
return (interfaceOrientation == UIInterfaceOrientationPortrait);
 }

 - (IBAction)buttonPressed:(id)sender {
[self.delegate addItem:self data:@"this is data"];

 }
 @end

ViewControllerB.h

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

@interface ViewControllerB : UIViewController<viewControllerADelegate>

@end

ViewControllerB.m

#import "ViewControllerB.h"
#import "ViewControllerA.h"

@interface ViewControllerB ()

@end

@implementation ViewControllerB

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

 - (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"MainStoryboard" bundle:nil];

ViewControllerA *vca = [storyboard instantiateViewControllerWithIdentifier:@"A"];
[vca setDelegate:self];

 }

- (void)viewDidUnload
 {
[super viewDidUnload];
// Release any retained subviews of the main view.
 }

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
 {
return (interfaceOrientation == UIInterfaceOrientationPortrait);
 }
-(void) addItem: (ViewControllerA *)controller data:(NSString *)item{
NSLog(@"delegate function called");
 }

 @end

我是不是错过了什么傻事？委托(delegate)方法 -(void) addItem: (ViewControllerA *)controller data:(NSString *)item 没有被触发。

最佳答案

您设计中的缺陷是尝试使用委托(delegate)将数据发送到您自己创建的对象。您当然不需要委托(delegate)，因为您可以使用简单的属性来完成。 myViewControllerBObject.dataProperty = @"some data"]; 就足够了。委托(delegate)通常用于将数据发送回创建当前对象的 Controller 或您应用中某处的任何其他 Controller 。

例如将ViewControllerA中的delegate代码移到ViewControllerB中，并添加一个UIButton和一个IBAction ViewControllerB 会将数据返回到ViewControllerA。开始了:

ViewControllerB.h

#import <UIKit/UIKit.h>

@class ViewControllerB;

@protocol viewControllerBDelegate <NSObject>

-(void) sendDataBack: (ViewControllerB *)controller data:(NSString *)item;

@end

@interface ViewControllerB : UIViewController
{
   __unsafe_unretained id <viewControllerBDelegate> delegate;
}

@property (nonatomic, assign) id<viewControllerBDelegate> delegate;
- (IBAction)buttonTouch:(id)sender;

@end

ViewControllerB.m

#import "ViewControllerB.h"

@interface ViewControllerB ()

@end

@implementation ViewControllerB
@synthesize delegate;
....
- (IBAction)buttonTouch:(id)sender {
    [self.delegate sendDataBack:self data:@"my data"];
}
@end

在 ViewControllerA 中，您首先需要通过 segues 获取推送的 ViewControllerB 对象。然后实现委托(delegate)方法。

ViewControllerA.h

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

@interface ViewControllerA : UIViewController <viewControllerBDelegate>
- (IBAction)buttonPressed:(id)sender;

@end

ViewControllerA.m

#import "ViewControllerA.h"

@interface ViewControllerA ()

@end

@implementation ViewControllerA
......
- (IBAction)buttonPressed:(id)sender {

}
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    NSLog(@"id %@", [segue destinationViewController]);
    ViewControllerB *vcb = (ViewControllerB *)[segue destinationViewController];
    vcb.delegate = self;  //key point
}
- (void)sendDataBack:(ViewControllerB *)controller data:(NSString *)item
{
    NSLog(@"Here is the data %@ and the controller it comes from %@", item, controller);
}
@end

希望这能帮助您更好地理解与委托(delegate)的沟通。

关于iphone - 我的自定义 View Controller 委托(delegate)不工作，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/11115913/