Runtime 实现动态添加属性

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利用动态加载为对象添加一个 block 点击属性;

.h 文件

 #import <UIKit/UIKit.h>

 @interface UIView (Tap)

 /**

  *  动态添加手势

  */

 - (void)setTapActionWithBlock:(void (^)(void))block ;

 @end

.m 文件

 #import "UIView+Tap.h"

 #import <objc/runtime.h>

 /**

  *  动态添加手势

  */

 static const char *ActionHandlerTapGestureKey;

 @implementation UIView (Tap)

 - (void)setTapActionWithBlock:(void (^)(void))block {

     self.userInteractionEnabled = YES;

     UITapGestureRecognizer *gesture = objc_getAssociatedObject(self, &ActionHandlerTapGestureKey);

     if (!gesture) {

         gesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleActionForTapGesture:)];

         [self addGestureRecognizer:gesture];

         objc_setAssociatedObject(self, &ActionHandlerTapGestureKey, gesture, OBJC_ASSOCIATION_RETAIN);

     }

     objc_setAssociatedObject(self, &ActionHandlerTapGestureKey, block, OBJC_ASSOCIATION_COPY);

 }

 - (void)handleActionForTapGesture:(UITapGestureRecognizer *)gesture {

     if (gesture.state == UIGestureRecognizerStateRecognized)  {

         void(^action)(void) = objc_getAssociatedObject(self, &ActionHandlerTapGestureKey);

         if (action)  {

             action();

         }

     }

 }

 @end