要求：在一个UIView界面中又一个lable和Button，想点击按钮之后改变lable的值，用协议委托实现

Protocol（ChangeText.h）:

#import <Foundation/Foundation.h>  @protocol ChangeText <NSObject>  -(void)change:(NSString *)val;  @end

Button.h:

#import <Foundation/Foundation.h> #import "ChangeText.h" @interface Button : NSObject  @property(nonatomic,retain) id<ChangeText> delegate;  -(void)changetext:(NSString *)str;  @end

Button.m:

#import "Button.h"  @implementation Button  -(void)changetext:(NSString *)val {     if ([_delegate respondsToSelector:@selector(change:)]) {         [_delegate change:val];     } }  - (void)dealloc {     [_delegate release];     [super dealloc]; }  @end

创建一个遵循协议的View

ViewA.h:

#import <Foundation/Foundation.h> #import "ChangeText.h" #import "Button.h" @interface ViewA : NSObject<ChangeText>  @property(nonatomic,retain)NSString* textValue; @property(nonatomic,retain)Button *btn;  //实现协议的change方法 -(void)change;  @end

View.m:

#import "ViewA.h"  @implementation ViewA  +viewAWithText:(NSString *)val {     ViewA *a = [[[ViewA alloc] init] autorelease];     a.textValue = @"text";     //初始化Button，并且将当前实现了协议的ViewA赋给button他的委托方法     Button *btn = [[[Button alloc] init] autorelease];     btn.delegate = a;     a.btn = btn;     return a; }  -(void)change:(NSString *)val {     self.textValue = val;     NSLog(@"当前的view中文本值是:%@",self.textValue); }  -(void)dealloc {     [_btn release];     [_textValue release];     [super dealloc]; }  @end

main:

#import <Foundation/Foundation.h> #import "ViewA.h" #import "Button.h" int main(int argc, const char * argv[]) {      @autoreleasepool {                  ViewA *view = [ViewA viewAWithText:@"text"];         NSLog(@"当然view中的文本值是:%@",view.textValue);         [view.btn changetext:@"lable"];     }     return 0; }

结果：

2013-08-05 17:23:22.754 按钮点击[2144:303] 当然view中的文本值是:text

2013-08-05 17:23:22.756 按钮点击[2144:303] 当前的view中文本值是:lable

本文转自蓬莱仙羽51CTO博客，原文链接：http://blog.51cto.com/dingxiaowei/1366464，如需转载请自行联系原作者