protocol的简单写法

//
//  TouchView.h
//  LessonUIControlAndSubClass



#import <UIKit/UIKit.h>

@class TouchView;
//1.制定协议，协议名字格式：类名+Delegate
@protocol TouchViewDelegate <NSObject>

@optional
- (void)touchBegan:(TouchView *)touchView;
- (void)touchMoved:(TouchView *)touchView;
- (void)touchEnded:(TouchView *)touchView;
- (void)touchCancelled:(TouchView *)touchView;

@end

@interface TouchView : UIView

//2.写属性，属性名delegate，类型是id,并且要遵守协议<类名Delegate>
@property (assign, nonatomic) id<TouchViewDelegate> delegate;

@end

---

//
//  TouchView.m
//  LessonUIControlAndSubClass
//

#import "TouchView.h"

@implementation TouchView

//3.一旦找到代理，让代理执行事情
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    //判断delegate是否实现了某方法
    if ([_delegate respondsToSelector:@selector(touchBegan:)]) {
        [_delegate touchBegan:self];
    }
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    if ([_delegate respondsToSelector:@selector(touchMoved:)]) {
        [_delegate touchMoved:self];
    }
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    if ([_delegate respondsToSelector:@selector(touchEnded:)]) {
        [_delegate touchEnded:self];
    }
}

- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {
    if ([_delegate respondsToSelector:@selector(touchCancelled:)]) {
        [_delegate touchCancelled:self];
    }
}

@end