通过给NSObject添加分类实现封装

使用时 对象 直接调用即可

-(void)sjyObserver:(NSObject *)object keyPath:(NSString *)keyPath block:(KVOBlock)block;

/*
 *   object : 观察者(一般使用 self ) 
 *   keyPath: 被观察的属性字段
 *   block  : 观察者方法回调实现
*/

例子

    Person *person = [[Person alloc] init];
    person.name = @"zhangsan";
    person.score = @84;

    [person sjyObserver:self keyPath:@"score" block:^{ 
    // 分数变化时实现代码
    
    NSLog(@"分数变化了");
    }];


    person.score = @65; // 重新给分数赋值时会执行block 内的处理

封装代码

.h 文件

#import <Foundation/Foundation.h>

typedef void(^KVOBlock)(void);
@interface NSObject (SJYKVO)

- (void)sjyObserver:(NSObject *)object keyPath:(NSString *)keyPath block:(KVOBlock)block;

@end

.m 文件

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

typedef void(^DeallocBlock)(void);
@interface EOCKVOController : NSObject

@property(nonatomic, strong)NSObject *observedObject;
@property(nonatomic, strong)NSMutableArray <DeallocBlock>*blockArr;

@end

@implementation EOCKVOController

-(NSMutableArray<DeallocBlock> *)blockArr {
    
    if (!_blockArr) {
        _blockArr = [NSMutableArray array];
    }
    return _blockArr;
    
}


//nextviewController -> kvoController
- (void)dealloc {
    
    ///对observedObject  removeObserver
    NSLog(@"kvoController dealloc");
    [_blockArr enumerateObjectsUsingBlock:^(DeallocBlock  _Nonnull block, NSUInteger idx, BOOL * _Nonnull stop) {
       
        block();
        
    }];
    
}

@end

@interface NSObject ()

@property(nonatomic, strong)NSMutableDictionary <NSString *, KVOBlock>*dict;
@property(nonatomic, strong)EOCKVOController *kvoController;

@end

@implementation NSObject (SJYKVO)

- (void)sjyObserver:(NSObject *)observer keyPath:(NSString *)keyPath block:(KVOBlock)block {
    self.dict[keyPath] = block;
    
    ///self已经持有了kvoController
    self.kvoController.observedObject = observer;
    
    __unsafe_unretained typeof(self)weakSelf = self;
    
    [self.kvoController.blockArr addObject:^{
       
        [observer removeObserver:weakSelf forKeyPath:keyPath];
        
    }];
    
    //监听
    [observer addObserver:self forKeyPath:keyPath options:NSKeyValueObservingOptionNew context:NULL];
    
}

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


////getter 和 setter方法
- (NSMutableDictionary<NSString *,KVOBlock> *)dict {
    
    NSMutableDictionary *tmpDict = objc_getAssociatedObject(self, @selector(dict));
    if (!tmpDict) {
        tmpDict = [NSMutableDictionary dictionary];
        objc_setAssociatedObject(self, @selector(dict), tmpDict, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    }
    return tmpDict;
    
}

- (EOCKVOController *)kvoController {
    
    EOCKVOController *tmpKvoController = objc_getAssociatedObject(self, @selector(kvoController));
    if (!tmpKvoController) {
        
        tmpKvoController = [[EOCKVOController alloc] init];
        objc_setAssociatedObject(self, @selector(kvoController), tmpKvoController, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
        
    }
    return tmpKvoController;
    
}
@end