objective-c协议代表 [英] objective-c protocol delegates

问题描述

我了解代表的工作原理，通过一些例子，但现在有一个基本的测试应用程序，似乎还没有得到它。

I'm understanding how delegates work, had gone trough some examples, but now with a basic app for testing, it seems i haven't yet got it,

这里我的代码：

类定义协议> * .h

Class defining protocol > *.h

#import <Foundation/Foundation.h>
@protocol protoPerra <NSObject>

-(void) dimeTuNombre:(NSString *) s;
@end

@interface MyClassic : NSObject {
id<protoPerra> _delegate;  
}
@property (assign) id<protoPerra> delegate;
@end

实现协议> * .m

Class implementing protocol> *.m

#importMyClassic.h

#import "MyClassic.h"

@implementation MyClassic
@synthesize delegate = _delegate;
- (id)init
{
self = [super init];
if (self) {
    // Initialization code here.
    [[self delegate] dimeTuNombre:@"pinguete"];
 }

return self;
}
-(void) dealloc {
[_delegate release];
_delegate = nil;
[super dealloc];
}
@end

类采用协议：

#importMyClassic.h
@interface MainViewController：UIViewController（protoPerra）

#import "MyClassic.h" @interface MainViewController : UIViewController (protoPerra)

.m

#import "MainViewController.h"

  @implementation MainViewController
  -(void) dimeTuNombre {
   NSLog(@"ss9!! tkt");
   }
   - (void)viewDidLoad {
[super viewDidLoad];

UILabel *lava = [[[UILabel alloc] initWithFrame:CGRectMake(30, 100, 100, 20)] autorelease];
lava.text = @"lava ss9";
[self.view addSubview:lava];

MyClassic *pirr = [[[MyClassic alloc] init ] autorelease];
[pirr setDelegate:self];
 }
 -(void) dimeTuNombre:(NSString *)s {
   NSLog(@"%@",s);
  }
  @end

所以在这个简单的例子中缺少什么它与我的代表一起工作？

so what is missing in this simple example to make it work with my delegate?

非常感谢！

请注意，我已经使用（）

Please note i have used () insted of the <> [in the .h of the adopting class] as if i use the Chevrons, the code disappears

推荐答案

你打电话给在MyClassic init中的委托方法（dimeTuNombre :)，但代理尚未设置，所以您需要重新思考什么时候调用dimeTuNombre：或重构MyClassic类以创建一个构造函数，如

You call the delegate method (dimeTuNombre:) in MyClassic init, but the delegate is not set yet, so you either need to rethink when to call dimeTuNombre:, or refactor the MyClassic class to have a constructor like

-(id)initWithDelegate:(id<protoPerra>)delegate

而不是简单的初始化。

要澄清，在当前的代码中，您可以在MainViewController.h中设置代理[pirr setDelegate：自]; - 将MyClassic属性的值delegate设置为MainViewController的当前实例。请注意，当您调用MyClassic的init时，代理尚未设置，因此[[self delegate] dimeTuNombre：@pinguete];调用不做任何事情（代理在这一点上为零）

To clarify, in your current code you set the delegate in MainViewController.h when you do [pirr setDelegate:self]; - which sets the value "delegate" of the property of MyClassic to the current instance of MainViewController. Note that when you call MyClassic's init, the delegate isn't set yet, so the [[self delegate] dimeTuNombre:@"pinguete"]; call does nothing (delegate is nil at that point).

您可以按照以下方式更改MyClassic构造函数：

You could change your MyClassic constructor as follows:

-(id)initWithDelegate:(id<protoPerra>)aDelegate
{
self = [super init];
if (self) {
    _delegate = aDelegate;
    // Initialization code here.
    [[self delegate] dimeTuNombre:@"pinguete"];
 }

return self;

}

而不是这样：

MyClassic *pirr = [[[MyClassic alloc] init ] autorelease];
[pirr setDelegate:self];

您将这样做：

MyClassic *pirr = [[[MyClassic alloc] initWithDelegate:self ] autorelease];

这将工作，但请注意，通常委托用于各种通知 - 如按钮报告它被点击或套接字说它已经收到一些数据。

This will work, but note that usually delegates are used for notifications of various kinds - like a button reporting it was clicked or a socket says it has received some data.

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