Block的示例学习

 @interface ViewController ()

 @property (weak, nonatomic) IBOutlet UIButton *btn;

 - (IBAction)reset:(id)sender;
 - (IBAction)run:(id)sender;
 - (IBAction)rotate:(id)sender;
 - (IBAction)scale:(id)sender;

 @end

 @implementation ViewController

 - (void)viewDidLoad {
     [super viewDidLoad];

 }

 //定义函数,参数是block类型 无返回值,无参数的block

 - (void)btnClickWithBlock:(void (^)())block
 {
     // 0.动画（头部-开始动画）
     [UIView beginAnimations:nil context:nil];
     // 设置动画的执行时间
     [UIView setAnimationDuration:1.0];

     //block的调用
     block();

     // 1.动画（尾部-提交动画-执行动画）
     [UIView commitAnimations];
 }

 - (void)didReceiveMemoryWarning {
     [super didReceiveMemoryWarning];
     // Dispose of any resources that can be recreated.
 }

 //重置
 - (IBAction)reset:(id)sender {

     [self btnClickWithBlock:^{
         _btn.transform = CGAffineTransformIdentity;
     }];
 }

 //行走
 - (IBAction)run:(id)sender {

     [self btnClickWithBlock:^{

         NSLog(@"self = %@",self);   //表示此控制器

         // 1.先取出frame
         CGPoint tempCenter = _btn.center;

         // 2.取出按钮的tag标记
         NSInteger tag = [sender tag];

         switch (tag) {
             case :

                 tempCenter.y -= kDelta;

                 break;

             case :

                 tempCenter.x -= kDelta;
                 break;

             case :

                 tempCenter.y += kDelta;
                 break;

             case :

                 tempCenter.x += kDelta;
                 break;

             default:
                 break;
         }

         // 3.重新赋值按钮的frame
         _btn.center = tempCenter;

     }];
 }

 //旋转
 - (IBAction)rotate:(id)sender {

     [self btnClickWithBlock:^{
         NSInteger tag = [sender tag];
         if ( == tag) { // 左
             _btn.transform = CGAffineTransformRotate(_btn.transform, M_PI_4 * -);
         } else { // 右
             _btn.transform = CGAffineTransformRotate(_btn.transform, M_PI_4 * );
         }
     }];

 }

 //缩放
 - (IBAction)scale:(id)sender {

     [self btnClickWithBlock:^{
         CGFloat scale = [sender tag] ==  ? 1.2 : 0.8;
         _btn.transform = CGAffineTransformScale(_btn.transform, scale, scale);
     }];

 }