KVO

Dog类.h:

@interface Dog : NSObject{

    NSString *dogName;

}

Person类.h:

#import "Dog.h"

@interface Person : NSObject{

    NSString *name;

    int age;

    Dog *dg;

}

Person *xiaowang = [[Person alloc]init];

        //使用KVC设置变量的值

        //使用之前必须知道变量的名字

        [xiaowang setValue:@"小王" forKey:@"name"];

        NSString *name = [xiaowang valueForKey:@"name"];

        NSLog(@"%@",name);

        

        //对类里面的某个对象变量的实行设置

        Dog *ww = [[Dog alloc]init];

        [xiaowang setValue:ww forKey:@"dg"];

        

        [xiaowang setValue:@"汪汪" forKeyPath:@"dg.dogName"];

        NSString *dgName = [xiaowang valueForKeyPath:@"dg.dogName"];

        NSLog(@"%@",dgName);

 KVO2:

CreatedCard类.h:

@interface CreatedCard : NSObject{

    int money;

}

Person类.h:

@property (nonatomic,strong)CreatedCard *card;

Person类.m:

-(void)dealloc{

    [_card release];

    [self removeObserver:self forKeyPath:@"card.money"];

    [super dealloc];

}

-(instancetype)init{

    if (self = [super init]) {

        self.card = [[[CreatedCard alloc]init]autorelease] ;

        //当前这个类添加一个监听器，监听card对象的money属性，监听这个属性变化之前之后的值

        [self addObserver:self forKeyPath:@"card.money" options:NSKeyValueObservingOptionOld|NSKeyValueObservingOptionNew context:nil];

    }

    return self;

}

//属性变化之后的回调

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSString *,id> *)change context:(void *)context{

    int oldValue = [[change objectForKey:NSKeyValueChangeOldKey]intValue];

    int newValue = [[change objectForKey:NSKeyValueChangeNewKey]intValue];

    NSLog(@"old:%d",oldValue);

    NSLog(@"new:%d",newValue);

}

 main:

#import <Foundation/Foundation.h>

#import "Person.h"

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

    @autoreleasepool {

        Person *xw = [[[Person alloc]init]autorelease];

        [xw setValue:@1000 forKeyPath:@"card.money"];

        [xw setValue:@2000 forKeyPath:@"card.money"];

    }

    return 0;

}