iphone开发中的手势操作：Pinches 捏合

用Automatic Gesture Recognition实现十分简单

- (void)viewDidLoad
{
    [super viewDidLoad];
    UIPinchGestureRecognizer *pinch = [[UIPinchGestureRecognizer alloc]
        initWithTarget:self action:@selector(doPinch:)];
    [self.view addGestureRecognizer:pinch];
}

- (void)doPinch:(UIPinchGestureRecognizer *)pinch {
    if (pinch.state == UIGestureRecognizerStateBegan) {
        initialFontSize = label.font.pointSize;
    } else {
        label.font = [label.font fontWithSize:initialFontSize * pinch.scale];
    }
}

@property (assign, nonatomic) CGFloat initialFontSize;

也可以自己实现，使用distanceBetweenPoints 可以知道两个点之间的距离。