KVC和KVO的区别

KVC和KVO

KV表示的是key，value

C是Coding，O是Observing(监听)

建一个Person的类

person.h文件

#import <Foundation/Foundation.h>
#import "WuGong.h"

@interface Person : NSObject
{
    //NSString *_name;
    //NSString *name;
}

@property (nonatomic,copy)NSString *name;
@property (nonatomic,strong)WuGong *wuGong;
//在Person类中定义一个wuGong的属性
@end

person.m文件

#import "Person.h"

@implementation Person
//没找到要赋值的key，就会调用，也是为了防止报错的时候程序会直接崩掉。
- (void)setValue:(id)value forUndefinedKey:(NSString *)key
{
    NSLog(@"没有找到%@",key);
}

- (id)valueForUndefinedKey:(NSString *)key
{
    NSLog( @"没有找到%@",key);
    return @"sdjfklsdj";
}
@end

ViewController.m文件

#import "ViewController.h"
#import "Person.h"

@interface ViewController ()
{
    Person *_person;
}

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    _person = [[Person alloc] init];
    //_person.name = @"ymj";
    //kvc赋值
    [_person setValue:@"ldd" forKey:@"name"];
    /*1.先找name的属性，找见赋值
        2.如果name属性没找见，就找_name的成员变量赋值
        3.如果_name 没有找到，就找name得成员变量赋值
        4.如果都没有找到，就调用- (void)setValue:(id)value forKey:(NSString *)key方法
     
     */
   
    //kvc取值
    //4.valueForUndefinedKey:
    NSLog(@"%@",[_person valueForKey:@"name"]);
    
    //第二种赋值
    _person.wuGong = [[WuGong alloc] init];
    _person.wuGong.name = @"葵花点穴手";
    [_person setValue:@"葵花点穴手" forKeyPath:@"wuGong.name"];
    //第三种赋值
    NSDictionary *dic = [NSDictionary dictionaryWithObject:@"紫萱" forKey:@"name"];
    [_person setValuesForKeysWithDictionary:dic];
    
    
    
    //KVO
    //self去监听——person里面的name有没有发生变化
    NSString *str = @"李逍遥";
       //因为context接收的时void类型，所以这里强转了一下
   [_person addObserver:self forKeyPath:@"name" options:NSKeyValueObservingOptionOld|NSKeyValueObservingOptionNew  context:(void *)str];
    _person.name = @"龙葵";
    //移除监听
    //[_person removeObserver:self forKeyPath:@""];
}

//监听到值发生改变 keyPath:监听的属性@"name"  Object:_person
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    NSString *str = (__bridge NSString *) context;//将接收的context值再转位NSString类型的
    NSLog(@"%@",str);
    NSLog(@"改变前的值:%@",change[@"old"]);
    NSLog(@"改变后的值:%@",change[@"new"]);
}

WuGong.h文件

#import <Foundation/Foundation.h>

@interface WuGong : NSObject
@property (nonatomic,copy)NSString *name;
@end