利用runtime实现对象关联

• 给UIBarButtonItem添加一个Block分类

#import <UIKit/UIKit.h>

@interface UIBarButtonItem (BlockSupport)

- (nullable instancetype)initWithTitle:(nullable NSString *)title style:(UIBarButtonItemStyle)style andBlock:(void(^)())clickBlock;

@end

#import "UIBarButtonItem+BlockSupport.h"
#import <objc/runtime.h>

const char *barbuttonItemBlockKey = "barbuttonItemBlockKey";

@implementation UIBarButtonItem (BlockSupport)

- (instancetype)initWithTitle:(nullable NSString *)title style:(UIBarButtonItemStyle)style andBlock:(void(^)())clickBlock
{
    self = [self initWithTitle:title style:style target:self action:@selector(handleClick)];
    if (self) {
        objc_setAssociatedObject(self, barbuttonItemBlockKey, clickBlock, OBJC_ASSOCIATION_COPY);
    }
    return self;
}

- (void)handleClick
{
    void (^block)() = objc_getAssociatedObject(self, barbuttonItemBlockKey);
    if (block ) {
        block();
    }
}

@end

.m实现是将外界传进来的clickBlock跟self进行关联

 objc_setAssociatedObject(self, barbuttonItemBlockKey, clickBlock, 

当点击Item对象的时候,执行handClick方法,在handClick方法通过self拿到外界传递进来的Block,并执行

 void (^block)() = objc_getAssociatedObject(self, barbuttonItemBlockKey);
    if (block ) {
        block();
}

下面使用我们经常处理按钮点击的常用方法来使用objc_setAssociatedObject实现

1.创建一个UIButton的分类

#import <UIKit/UIKit.h>

@interface UIButton (Block)

- (void)addBlock:(void(^)())clickBlock;
@end

#import "UIButton+Block.h"
#import <objc/runtime.h>

const char *buttonBlockKey = "buttonBlockKey";

@implementation UIButton (Block)

- (void)addBlock:(void(^)())clickBlock
{
    [self addTarget:self action:@selector(handleClick) forControlEvents:UIControlEventTouchUpInside];
    objc_setAssociatedObject(self, buttonBlockKey, clickBlock, OBJC_ASSOCIATION_COPY);
    
    
}

- (void)handleClick
{
    void (^block)() = objc_getAssociatedObject(self, buttonBlockKey);
    if (block ) {
        block();
    }
}
@end

那么我们在代码中监听按钮的点击事件

[btn addBlock:^{
// 当按钮被点击执行的代码
        NSLog(@"-------");
    }];