UIPinchGestureRecognizer缩放手势添加缩放

///上一次缩放比例,默认为1
@property (nonatomic, assign) CGFloat lastScale;
///最大缩放比例,默认为2
@property (nonatomic, assign) CGFloat maxScale;
///最小缩放比例,默认为1
@property (nonatomic, assign) CGFloat minScale;

//设置缩放比例
self.lastScale = 1;
self.minScale = 1;
self.maxScale = 2;

- (void)pinchGestureRecognizer:(UIPinchGestureRecognizer *)recognizer {
    switch (recognizer.state) {
        case UIGestureRecognizerStateBegan://缩放开始
        case UIGestureRecognizerStateChanged://缩放改变
        {
            CGFloat currentScale = [[self.layer valueForKeyPath:@"transform.scale"] floatValue];
            CGFloat newScale = recognizer.scale - self.lastScale + 1;
            newScale = MIN(newScale, self.maxScale / currentScale);
            newScale = MAX(newScale, self.minScale / currentScale);
            
            self.transform = CGAffineTransformScale(self.transform, newScale, newScale);

            self.lastScale = recognizer.scale;
        }
            break;
        case UIGestureRecognizerStateEnded://缩放结束
            self.lastScale = 1;
            break;
            
        default:
            break;
    }
}