//委托的协议定义@protocol UpdateDelegate <NSObject>- (void)update;@end@interface Test : NSObject//委托变量定义@property (nonatomic, weak) id<UpdateDelegate> delegate;//blocktypedef void (^UpdateBlock)(id obj);@property (nonatomic, copy) UpdateBlock updateBlock;- (void) startTest;   @end@implementation Test- (void) startTest{    [NSTimer scheduledTimerWithTimeInterval:3.0f target:self selector:@selector(scheduledEnd) userInfo:nil repeats:NO];}- (void)scheduledEnd{    [self.delegate update];//委托        //block    if (self.updateBlock)    {        self.updateBlock(@"test");    }}@end// 实现- (void)viewDidLoad{    [super viewDidLoad];    Test *test = [[Test alloc] init];    test.delegate = self; //设置委托实例        //实现block    test.updateBlock = ^(id obj)    {        UIAlertView *alert=[[UIAlertView alloc] initWithTitle:@"提示" message:obj delegate:self cancelButtonTitle:nil otherButtonTitles:@"确定",nil];                alert.alertViewStyle=UIAlertViewStyleDefault;        [alert show];    };        [test startTest];//启动定时器}//"被委托对象"实现协议声明的方法,由"委托对象"调用- (void)update{    UIAlertView *alert=[[UIAlertView alloc] initWithTitle:@"提示" message:@"时间到" delegate:self cancelButtonTitle:nil otherButtonTitles:@"确定",nil];        alert.alertViewStyle=UIAlertViewStyleDefault;    [alert show];}