测试代码:

01.png

测试结果:

02.png

#import <Foundation/Foundation.h>

typedef void(^kvoBlock)(id oldValue,id newValue);

@interface NSObject (KVO)

/**
 <#Description#>

 @param observer 被观察对象
 @param keyPath 被观察的属性
 @param block 属性值改变触发的操作
 */
-(void)addObserver:(NSObject *)observer
        forKeyPath:(NSString *)keyPath
          kvoBlock:(kvoBlock)block;

@end

#import "NSObject+KVO.h"
#import <objc/runtime.h>

typedef void(^deallocBlock)(void);
@interface KVOController: NSObject

@property (nonatomic,strong) NSObject *observeredObj;

@property (nonatomic,strong) NSMutableArray<deallocBlock> *blockArr;

@end

@implementation KVOController

-(NSMutableArray<deallocBlock> *)blockArr{
    if (!_blockArr) {
        _blockArr = @[].mutableCopy;
    }
    return _blockArr;
}

-(void)dealloc{
    NSLog(@"KVOController dealloc");
    
    [self.blockArr enumerateObjectsUsingBlock:^(deallocBlock  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        obj();
    }];
}

@end


// 根据观察者，被观察者，keyPath拼成唯一的字典的key
#define KEYPATH(a, b, c) [NSString stringWithFormat:@"%@-%@-%@",[a class], [b class], c]

@interface NSObject ()

@property (nonatomic,strong) NSMutableDictionary<NSString *,kvoBlock> *dict;

@property (nonatomic,strong) KVOController *kvoController;

@end

@implementation NSObject (KVO)

-(void)addObserver:(NSObject *)observer
        forKeyPath:(NSString *)keyPath
          kvoBlock:(kvoBlock)block{
    
    self.dict[KEYPATH(self, observer, keyPath)] = block;
    
    self.kvoController.observeredObj = observer;
    
    __unsafe_unretained typeof(self) weakSelf = self;
    [self.kvoController.blockArr addObject:^{
        
        [observer removeObserver:weakSelf forKeyPath:keyPath];
        
    }];

//    NSLog(@"observer = %@",observer);
//    NSLog(@"self = %@",self);
    
    [observer addObserver:self
           forKeyPath:keyPath
              options:NSKeyValueObservingOptionOld | NSKeyValueObservingOptionNew
              context:NULL];
    
    
}

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context{
    
    kvoBlock block = self.dict[KEYPATH(self, object, keyPath)];
    if (block) {
        block([change valueForKey:NSKeyValueChangeOldKey], [change valueForKey:NSKeyValueChangeNewKey]);
    }
}


-(NSMutableDictionary<NSString *,kvoBlock> *)dict{
    NSMutableDictionary *tmpDic = objc_getAssociatedObject(self, @selector(dict));
    if (!tmpDic) {
        tmpDic = @{}.mutableCopy;
        objc_setAssociatedObject(self, @selector(dict), tmpDic, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    }
    return tmpDic;
}

-(KVOController *)kvoController{
    KVOController *kvoController = objc_getAssociatedObject(self, @selector(kvoController));
    if (!kvoController) {
        kvoController = [KVOController new];
        objc_setAssociatedObject(self, @selector(kvoController), kvoController, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    }
    return kvoController;
}

@end