protocol的简单写法

 1 //
 2 //  TouchView.h
 3 //  LessonUIControlAndSubClass
 4
 5
 6
 7 #import <UIKit/UIKit.h>
 8
 9 @class TouchView;
10 //1.制定协议，协议名字格式：类名+Delegate
11 @protocol TouchViewDelegate <NSObject>
12
13 @optional
14 - (void)touchBegan:(TouchView *)touchView;
15 - (void)touchMoved:(TouchView *)touchView;
16 - (void)touchEnded:(TouchView *)touchView;
17 - (void)touchCancelled:(TouchView *)touchView;
18
19 @end
20
21 @interface TouchView : UIView
22
23 //2.写属性，属性名delegate，类型是id,并且要遵守协议<类名Delegate>
24 @property (assign, nonatomic) id<TouchViewDelegate> delegate;
25
26 @end

 1 //
 2 //  TouchView.m
 3 //  LessonUIControlAndSubClass
 4 //
 5
 6 #import "TouchView.h"
 7
 8 @implementation TouchView
 9
10 //3.一旦找到代理，让代理执行事情
11 - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
12     //判断delegate是否实现了某方法
13     if ([_delegate respondsToSelector:@selector(touchBegan:)]) {
14         [_delegate touchBegan:self];
15     }
16 }
17
18 - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
19     if ([_delegate respondsToSelector:@selector(touchMoved:)]) {
20         [_delegate touchMoved:self];
21     }
22 }
23
24 - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
25     if ([_delegate respondsToSelector:@selector(touchEnded:)]) {
26         [_delegate touchEnded:self];
27     }
28 }
29
30 - (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {
31     if ([_delegate respondsToSelector:@selector(touchCancelled:)]) {
32         [_delegate touchCancelled:self];
33     }
34 }
35
36 @end