ios delegate 和 block

//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;

//block
typedef 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];
}