Runtime 实现 动态添加属性

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