iOS-扩大按钮点击范围

利用runtime和- (nullable UIView *)hitTest:(CGPoint)point withEvent:(nullable UIEvent *)event;
方法给UIButton添加一个Category扩展按钮的点击范围

#import 

@interface UIButton (ICECategory)

- (void)expandClickAreaWithTop:(NSInteger)_top Right:(NSInteger)_right Bottom:(NSInteger)_bottom Left:(NSInteger)_left;

@end

#import "UIButton+ICECategory.h"
#import 

@implementation UIButton (ICECategory)

static char topNameKey;
static char rightNameKey;
static char bottomNameKey;
static char leftNameKey;

/*
 objc_setAssociatedObject(id _Nonnull object, const void * _Nonnull key,id _Nullable value, objc_AssociationPolicy policy)
 
 key：要保证全局唯一，key与关联的对象是一一对应关系。必须全局唯一。通常用@selector(methodName)作为key。
 value：要关联的对象。
 policy：关联策略。有五种关联策略。
 OBJC_ASSOCIATION_ASSIGN           等价于 @property(assign)。
 OBJC_ASSOCIATION_RETAIN_NONATOMIC 等价于 @property(strong, nonatomic)。
 OBJC_ASSOCIATION_COPY_NONATOMIC   等价于@property(copy, nonatomic)。
 OBJC_ASSOCIATION_RETAIN           等价于@property(strong,atomic)。
 OBJC_ASSOCIATION_COPY             等价于@property(copy, atomic)。
 */
- (void)expandClickAreaWithTop:(NSInteger)_top Right:(NSInteger)_right Bottom:(NSInteger)_bottom Left:(NSInteger)_left {
    objc_setAssociatedObject(self, &topNameKey, [NSNumber numberWithInteger:_top], OBJC_ASSOCIATION_COPY_NONATOMIC);
    objc_setAssociatedObject(self, &rightNameKey, [NSNumber numberWithInteger:_right], OBJC_ASSOCIATION_COPY_NONATOMIC);
    objc_setAssociatedObject(self, &bottomNameKey, [NSNumber numberWithInteger:_bottom], OBJC_ASSOCIATION_COPY_NONATOMIC);
    objc_setAssociatedObject(self, &leftNameKey, [NSNumber numberWithInteger:_left], OBJC_ASSOCIATION_COPY_NONATOMIC);
}

- (CGRect)expandedClickAre {
    NSNumber *topNum    = objc_getAssociatedObject(self, &topNameKey);
    NSNumber *rightNum  = objc_getAssociatedObject(self, &rightNameKey);
    NSNumber *bottomNum = objc_getAssociatedObject(self, &bottomNameKey);
    NSNumber *leftNum   = objc_getAssociatedObject(self, &leftNameKey);
    if (topNum && rightNum && bottomNum && leftNum) {
        return CGRectMake(self.bounds.origin.x - leftNum.integerValue, self.bounds.origin.y - topNum.integerValue, self.bounds.size.width + leftNum.integerValue + rightNum.integerValue, self.bounds.size.height + topNum.integerValue + bottomNum.integerValue);
    }
    else {
        return self.bounds;
    }
}

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