基于kvo的观察者模式

以下是我自己写的代码，方便新手理解kvo模式的流程。

思路，创建Person类，年龄属性，

show类负责显示Person对象，年龄显示的变化。

用kvo模式。

#import <Foundation/Foundation.h>

#import "Person.h"

#import "Show.h"

int main(int argc,const char * argv[]) {

    

   Person *p = [[Personalloc]init];

    

    p.age=11;

    

   Show *s = [[Showalloc]initWithPerson:p];

    

    [p setValue:@22forKey:@"age"];

    [p setValue:@23forKey:@"age"];

    

    

   // NSLog(@"%ld",p.age);

   return 0;

}

--------------------

#import <Foundation/Foundation.h>

@interface Person :NSObject

@property(nonatomic,copy)NSString *name;

@property(nonatomic,assign)NSInteger age;

@end

--------------------

#import "Person.h"

@implementation Person

@end

--------------------

#import <Foundation/Foundation.h>

#import "Person.h"

@interface Show : NSObject

@property(nonatomic,retain)Person *person;

- (id)initWithPerson:(Person *)per;

@end

------------------------

#import "Show.h"

@implementation Show

- (id)initWithPerson:(Person *)per{

   self = [superinit];

    

   if(self){

       _person = per;

        /*注意这里：把创建的per对象，即p，赋值给show里面的Person类属性，即设置，要拿出来还要生成get方法，所以这里不能简单的写个属性，直接@property（）即可。*/

        //_person = [per retain];

        

        [_personaddObserver:selfforKeyPath:@"age"options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOldcontext:nil];

        

    

    }

    return self;

}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context

{

   if([keyPath isEqualToString:@"age"]){

        

   NSNumber *age = [change objectForKey:@"new"];

    

   NSInteger newage = [age integerValue];

    

   NSLog(@"现在的age是%ld",newage);

    }else{

    

       NSLog(@"error");

    }

    

}

- (void)dealloc{

    [_personremoveObserver:selfforKeyPath:@"age"];

    

}

@end