extend view's touch area

UIView+ZDTouchExtendInsets

static const void *TouchExtendInsetKey = &TouchExtendInsetKey;

static void Swizzle(Class c, SEL orig, SEL new) {
    Method origMethod = class_getInstanceMethod(c, orig);
    Method newMethod = class_getInstanceMethod(c, new);
    if (class_addMethod(c, orig, method_getImplementation(newMethod), method_getTypeEncoding(newMethod))){
        class_replaceMethod(c, new, method_getImplementation(origMethod), method_getTypeEncoding(origMethod));
    }
    else {
        method_exchangeImplementations(origMethod, newMethod);
    }
}

@interface UIView() (ZDTouchExtendInsets)

@property (nonatomic, assign) UIEdgeInsets zd_touchExtendInsets;

@end


@implementation UIView (ZDTouchExtendInsets)

+ (void)load {
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        Swizzle(self, @selector(pointInside:withEvent:), @selector(zdPointInside:withEvent:));
    });
}

#pragma mark TouchExtendInset

- (BOOL)zdPointInside:(CGPoint)point withEvent:(UIEvent *)event {
    if (UIEdgeInsetsEqualToEdgeInsets(self.zd_touchExtendInsets, UIEdgeInsetsZero) || self.hidden) {
        return [self zdPointInside:point withEvent:event];
    }
    CGRect hitFrame = UIEdgeInsetsInsetRect(self.bounds, self.zd_touchExtendInsets);
    hitFrame.size.width = MAX(hitFrame.size.width, 0);
    hitFrame.size.height = MAX(hitFrame.size.height, 0);
    return CGRectContainsPoint(hitFrame, point);
}

- (void)setZd_touchExtendInsets:(UIEdgeInsets)zd_touchExtendInsets {
    UIEdgeInsets zdTouchExtendInsets = UIEdgeInsetsMake(-zd_touchExtendInsets.top, -zd_touchExtendInsets.left, -zd_touchExtendInsets.bottom, -zd_touchExtendInsets.right);
    objc_setAssociatedObject(self, TouchExtendInsetKey, [NSValue valueWithUIEdgeInsets:zdTouchExtendInsets], OBJC_ASSOCIATION_RETAIN);
}

- (UIEdgeInsets)zd_touchExtendInsets {
    return [objc_getAssociatedObject(self, TouchExtendInsetKey) UIEdgeInsetsValue];
}

@end