Objective-C利用协议实现回调函数

实现的代码如下：

定义协议：

#import <UIKit/UIKit.h>
@protocol NoteDelegate
//回调函数
-(void)messageCallBack:(NSString *)string;
@end
//调用协议
    #import <Foundation/Foundation.h>
    #import "NoteDelegate.h"
    @interface ManagerMessage : NSObject {
        id<NoteDelegate> *noteDelegate;
    }
    @property (nonatomic,retain) id<NoteDelegate> *noteDelegate;
    -(void)startThread;
    @end

#import "ManagerMessage.h"
    @implementation ManagerMessage
    @synthesize noteDelegate;
    //开始一个线程
    -(void)startThread
    {

        [NSTimer scheduledTimerWithTimeInterval:3
                                         target:self
                                       selector:@selector(targetMethod:)
                                       userInfo:nil
                                        repeats:NO];
    }
    -(void)targetMethod:(NSString *)string
    {
        if (self.noteDelegate!=nil) {
            //完成线程 调用回调函数
            [self.noteDelegate messageCallBack:@"回调函数"];
            }
    }
    @end

前台页面实现：

    #import "IphoneDeleteViewController.h"
    #import "ManagerMessage.h"
    @implementation IphoneDeleteViewController
    @synthesize textView;

    //回调函数
    -(void)messageCallBack:(NSString *)string
    {
        self.textView.text=string;
    }

    - (void)viewDidLoad {
        [super viewDidLoad];
        self.textView.text=@"测试";
        ManagerMessage *message=[[ManagerMessage alloc] init];
        //通知调用协议
        message.noteDelegate=self;
        [message startThread];
        [message release];
    }

    - (void)didReceiveMemoryWarning {
        [super didReceiveMemoryWarning];
    }

    - (void)viewDidUnload {
        self.textView=nil;
    }

    - (void)dealloc {
        [self.textView release];
        [super dealloc];
    }

    @end

通过以上几步我们基本可以实现回调函数的实现