OC-runtime

#import "UIButton+Enlarge.h"
#import <objc/runtime.h>


static char topEdgeKey;
static char leftEdgeKey;
static char bottomEdgeKey;
static char rightEdgeKey;

@implementation UIButton (Enlarge)

- (void)setEnlargedEdge:(CGFloat)enlargedEdge {
    [self setEnlargedEdgeWithTop:enlargedEdge left:enlargedEdge bottom:enlargedEdge right:enlargedEdge];
}

- (CGFloat)enlargedEdge {
    return [(NSNumber *)objc_getAssociatedObject(self, &topEdgeKey) floatValue];
}

- (void)setEnlargedEdgeWithTop:(CGFloat)top left:(CGFloat)left bottom:(CGFloat)bottom right:(CGFloat)right {
    objc_setAssociatedObject(self, &topEdgeKey, [NSNumber numberWithFloat:top], OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    objc_setAssociatedObject(self, &leftEdgeKey, [NSNumber numberWithFloat:left], OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    objc_setAssociatedObject(self, &bottomEdgeKey, [NSNumber numberWithFloat:bottom], OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    objc_setAssociatedObject(self, &rightEdgeKey, [NSNumber numberWithFloat:right], OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (CGRect)enlargedRect {
    NSNumber *topEdge = objc_getAssociatedObject(self, &topEdgeKey);
    NSNumber *leftEdge = objc_getAssociatedObject(self, &leftEdgeKey);
    NSNumber *bottomEdge = objc_getAssociatedObject(self, &bottomEdgeKey);
    NSNumber *rightEdge = objc_getAssociatedObject(self, &rightEdgeKey);
    if (topEdge && leftEdge && bottomEdge && rightEdge) {
        CGRect enlargedRect = CGRectMake(self.bounds.origin.x-leftEdge.floatValue, self.bounds.origin.y-topEdge.floatValue, self.frame.size.width+leftEdge.floatValue + rightEdge.floatValue, self.frame.size.height+topEdge.floatValue+bottomEdge.floatValue);
        return enlargedRect;
    } else {
        return self.bounds;
    }
}

- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event {
    if (self.alpha <=0.01 || !self.userInteractionEnabled || self.hidden) {
        return nil;
    }
    
    CGRect enlargedRect = [self enlargedRect];
    return CGRectContainsPoint(enlargedRect, point) ? self : nil;
}
@end



//子类重写
- (UIView*)hitTest:(CGPoint) point withEvent:(UIEvent*) event
{
    CGRect rect = [self enlargedRect];
    if (CGRectEqualToRect(rect, self.bounds))
    {
        return [super hitTest:point withEvent:event];
    }
    return CGRectContainsPoint(rect, point) ? self : nil;
}