1. UIPinchGestureRecognizer（捏合）基本介绍

• 父类是UIGestureRecognizer

2. UIPinchGestureRecognizer应用举例

- (void)setUpPinch
{
    // 捏合
    UIPinchGestureRecognizer *pinch = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(pinch:)];
    pinch.delegate = self;


    [self.imageView addGestureRecognizer:pinch];
}

- (void)pinch:(UIPinchGestureRecognizer *)pinch
{
    NSLog(@"%f",pinch.scale);
    self.imageView.transform = CGAffineTransformScale(self.imageView.transform, pinch.scale, pinch.scale);

    // 复位
    pinch.scale = 1;

}

3. UIPinchGestureRecognizer属性

// 伸缩比例
@property (nonatomic)          CGFloat scale;

// 伸缩速度
@property (nonatomic,readonly) CGFloat velocity;