ios扩大按钮的点击区域

面试的时候，有一次被问到怎样扩大Button的点击区域，当时回答的不是让面试官很满意，现在来总结一下。
在网上看了很多的方法，最后看到一篇关于用Rutime机制来实现的方法，真的很好用 参考文章
话不多说，上代码
一、创建一个button的分类
button.h文件

#import <UIKit/UIKit.h>
#import <objc/runtime.h>

@interface UIButton (ExpandTheClickArea)

- (void)setEnlargeEdge:(CGFloat) size;

- (void)setEnlargeEdgeWithTop:(CGFloat) top right:(CGFloat) right bottom:(CGFloat) bottom left:(CGFloat) left;

@end

button.m文件

#import "UIButton+ExpandTheClickArea.h"

@implementation UIButton (ExpandTheClickArea)

static char topNameKey;

static char rightNameKey;

static char bottomNameKey;

static char leftNameKey;



- (void)setEnlargeEdge:(CGFloat) size

{
    
    objc_setAssociatedObject(self, &topNameKey, [NSNumber numberWithFloat:size], OBJC_ASSOCIATION_COPY_NONATOMIC);
    
    objc_setAssociatedObject(self, &rightNameKey, [NSNumber numberWithFloat:size], OBJC_ASSOCIATION_COPY_NONATOMIC);
    
    objc_setAssociatedObject(self, &bottomNameKey, [NSNumber numberWithFloat:size], OBJC_ASSOCIATION_COPY_NONATOMIC);
    
    objc_setAssociatedObject(self, &leftNameKey, [NSNumber numberWithFloat:size], OBJC_ASSOCIATION_COPY_NONATOMIC);
    
}

- (void)setEnlargeEdgeWithTop:(CGFloat) top right:(CGFloat) right bottom:(CGFloat) bottom left:(CGFloat) left

{
    
    objc_setAssociatedObject(self, &topNameKey, [NSNumber numberWithFloat:top], OBJC_ASSOCIATION_COPY_NONATOMIC);
    
    objc_setAssociatedObject(self, &rightNameKey, [NSNumber numberWithFloat:right], OBJC_ASSOCIATION_COPY_NONATOMIC);
    
    objc_setAssociatedObject(self, &bottomNameKey, [NSNumber numberWithFloat:bottom], OBJC_ASSOCIATION_COPY_NONATOMIC);
    
    objc_setAssociatedObject(self, &leftNameKey, [NSNumber numberWithFloat:left], OBJC_ASSOCIATION_COPY_NONATOMIC);
    
}
- (CGRect)enlargedRect

{
    
    NSNumber* topEdge = objc_getAssociatedObject(self, &topNameKey);
    
    NSNumber* rightEdge = objc_getAssociatedObject(self, &rightNameKey);
    
    NSNumber* bottomEdge = objc_getAssociatedObject(self, &bottomNameKey);
    
    NSNumber* leftEdge = objc_getAssociatedObject(self, &leftNameKey);
    
    if (topEdge && rightEdge && bottomEdge && leftEdge)
        
    {
        
        return CGRectMake(self.bounds.origin.x - leftEdge.floatValue,
                          
                          self.bounds.origin.y - topEdge.floatValue,
                          
                          self.bounds.size.width + leftEdge.floatValue + rightEdge.floatValue,
                          
                          self.bounds.size.height + topEdge.floatValue + bottomEdge.floatValue);
        
    }
    
    else
        
    {
        
        return self.bounds;
        
    }
    
}

- (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;
    
}

@end

实现

#import "ViewController.h"
#import "UIButton+ExpandTheClickArea.h"
@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
   
    UIButton *btnCancel = [UIButton buttonWithType:UIButtonTypeCustom];
    
    btnCancel.frame = CGRectMake(100, 100, 10, 10);
    
    btnCancel.backgroundColor = [UIColor redColor];
    
    //在此可以随意设置button上下左右的点击范围
    [btnCancel setEnlargeEdgeWithTop:10 right:10 bottom:10 left:0];
    
    [btnCancel addTarget:self action:@selector(ExpandTheArea) forControlEvents:UIControlEventTouchUpInside];
    
    [self.view addSubview:btnCancel];
}
-(void)ExpandTheArea{

      NSLog(@"哈哈");
}
@end

二、什么是objc_setAssociatedObject

iOS objc_setAssociatedObject 关联对象的学习