Protocol协议 按钮点击

#import <Foundation/Foundation.h>
@class  Button;

//<>表示实现了某个协议
@protocol ButtonDelegate <NSObject>
-(void)onClick:(Button *)btn;
@end

@interface Button : NSObject
//delegate就是按钮的监听器  <>里面就是指上面的那个协议
@property(nonatomic,retain) id<ButtonDelegate> delegate;
-(void)click;
@end

#import "Button.h"

@implementation Button

-(void)click{
    //如果delegate实现了onclick：这个方法
    if([_delegate respondsToSelector:@selector(onClick:)])
    {
        //按钮被点击了，就应该通知监听器
        [_delegate onClick:self];
    }
    else
    {
        NSLog(@"监听器并没有实现onClick:方法");
    }
}

-(void)dealloc{
    [_delegate release];
    [super dealloc];
}
@end

#import <Foundation/Foundation.h>
#import "Button.h"

@interface MyListener : NSObject<ButtonDelegate>

@end

#import "MyListener.h"
#import "Button.h"

@implementation MyListener
-(void)onClick:(Button *)btn{
    NSLog(@"已经监听到按钮：%@点击了",btn);
}
@end

#import <Foundation/Foundation.h>
#import "Button.h"
//一个类要遵守一个协议，要用<>来添加协议名称
@interface ButtonListener : NSObject<ButtonDelegate>

@end

#import "ButtonListener.h"

@implementation ButtonListener
-(void)onClick{
    NSLog(@"按钮被点击了");
}
@end

#import <Foundation/Foundation.h>
#import "Button.h"
#import "ButtonListener.h"
#import "MyListener.h"

int main(int argc, const char * argv[])
{

    @autoreleasepool {
        //初始化一个按钮
        Button *btn=[[[Button alloc] init] autorelease];
        //初始化一个按钮监听器
        ButtonListener *btnListener=[[[ButtonListener alloc] init] autorelease];
        MyListener * mylisten=[[[MyListener alloc] init] autorelease];
        //将这个监听器给按钮
        btn.delegate=btnListener;
        [btn click];
        NSLog(@"当前按钮是%@",btn);
        btn.delegate=mylisten;
        [btn click];
    }
    return 0;
}

2013-08-02 14:47:26.352 Protocol[656:303] 监听器并没有实现onClick:方法

2013-08-02 14:47:26.353 Protocol[656:303] 当前按钮是<Button: 0x100109940>

2013-08-02 14:47:26.354 Protocol[656:303] 已经监听到按钮：<Button: 0x100109940>点击了