关于object-c的@protocol的理解

@protocol mytestClass <NSObject>- (void) callback:(int) num;@end@interface DiscoveryController : UIViewController<mytestClass>{    UIImageView *imageView;    }-(UIImage *) getImageFromURL:(NSString *)fileURL;@end

@interface MyCallBack : NSObject{    id<mytestClass> deleage;}@property(nonatomic,retain) id<mytestClass> deleage;- (void)setRun;@end

////  MyCallBack.m//  ACMobile////  Created by mr.liang on 15/1/22.//  Copyright (c) 2015年 mr.liang. All rights reserved.//#import "MyCallBack.h"@implementation MyCallBack@synthesize deleage;- (void) runThread{    NSLog(@"我在运行");    [NSThread sleepForTimeInterval:2];    [deleage callback:1];}- (void)setRun{    NSThread *callbackthread = [[NSThread alloc] initWithTarget:self selector:@selector(runThread) object:nil];    [callbackthread start];}@end

    MyCallBack *vv = [[MyCallBack alloc] init];    vv.deleage = self;    [vv setRun];