KVC 底层原理详解

KVC 其实就是键值编码  

1、赋值其实就两个方法 

• setValue: forKey 给对象的某个属性值赋值

• setValue:forKeyPath

  给对象的某个属性中的属性赋值

2、获取值其实也是两个方法

• valueForKey 获取对象的某个属性值

• valueForKeyPath 获取对象的某个属性中的属性值

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

@interface Person : NSObject
@property (nonatomic,assign) int age;
@property (nonatomic, strong) Cat *cat;
@end


  self.p=[[Person alloc]init];
    Cat *cat=[[Cat alloc]init];
    self.p.cat=cat;
    [self.p setValue:@12 forKey:@"age"];
    [self.p setValue:@"猪" forKeyPath:@"cat.name"];
    NSLog(@"--%d--%@",self.p.age,self.p.cat.name);//--12--猪
    
     NSLog(@"--%@--%@",[self.p valueForKey:@"age"],[self.p valueForKeyPath:@"cat.name"]);//--12--猪

3、setValue:forKey:的原理

 4、valueForKey:的原理

  self.p=[[Person alloc]init];
   [self.p setValue:@12 forKey:@"age"];

#import "Person.h"

@implementation Person
-(void)setAge:(int)age{
    NSLog(@"1");
}
-(void)_setAge:(int)age{
    NSLog(@"2");
}
@end

@interface Person : NSObject
{
    int _age;
    int _isAge;
    int  age;
    int isAge;
}
@end

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

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

@implementation Person
-(int)getAge{
    return 1;
}
-(int)age{
    return 2;
}
-(int)isAge{
    return 3;
}
-(int)_age{
    return 4;
}
@end

.h
@interface Person : NSObject
{
    int _age;
    int _isAge;
    int  age;
    int isAge;
}