延展+runtime 实现button block

目的: 以block的形式给button添加点击事件

使用：

 UIButton *btn=[UIButton buttonWithType:UIButtonTypeSystem];
[btn setTitle:title forState:UIControlStateNormal];
[btn addEventHandler:^(id sender) {
      
    } forControlEvents:UIControlEventValueChanged];

实现：

.h

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

typedef void (^ActionBlock)(id sender);

@interface UIControl (Blocks)

- (void)addEventHandler:(ActionBlock)handler forControlEvents:(UIControlEvents)controlEvents;

@end

.m

#import "UIControl+Blocks.h"

static char UIButtonHandlerKey;

@implementation UIControl (Blocks)

- (void)addEventHandler:(ActionBlock)handler forControlEvents:(UIControlEvents)controlEvents
{
    objc_setAssociatedObject(self, &UIButtonHandlerKey, handler, OBJC_ASSOCIATION_COPY_NONATOMIC);
    [self addTarget:self action:@selector(callActionHandler:) forControlEvents:controlEvents];
}


- (void)callActionHandler:(id)sender
{
    ActionBlock handler = (ActionBlock)objc_getAssociatedObject(self, &UIButtonHandlerKey);
    if (handler) {
        handler(sender);
    }
}

@end