目 录：
一、KVC
二、KVO
一、KVC机制
1、KVC简述
KVC是KeyValueCoding（键值对的编码）的简称，它是一种可以直接通过字符串的名字(key)来访问类属性(实例变量)的机制。而不是通过调用Setter、Getter方法访问。KVO 就是基于 KVC 实现的关键技术之一。
2，使用方法
关键方法定义在：NSKeyValueCodingprotocol。
KVC支持类对象和内建基本数据类型。
KVC的常用方法：
- (id)valueForKey:(NSString *)key;//获取
-(void)setValue:(id)value forKey:(NSString *)key;//设置
valueForKey的方法根据key的值读取对象的属性，setValue:forKey:是根据key的值来写对象的属性。
例如：
[person setValue:@“Tom” forKey:@“name”];
NSString *name = [person valueForKey:@“name”];
#import <Foundation/Foundation.h> @interface Person : NSObject
{
NSString *_name;
NSInteger _age;
Person *_wife;
}
@end
#import "ViewController.h"
#import "Person.h"
@interface ViewController () @end @implementation ViewController - (void)viewDidLoad {
[super viewDidLoad];
//创建对象
Person *person = [[Person alloc]init];
//使用KVC来存储对象的数据成员
[person setValue:@"Tom" forKey:@"_name"];
[person setValue:@ forKey:@"_age"];
NSLog(@"person:%@",person);
//取对象的数据成员
NSString *name = [person valueForKey:@"_name"];
NSInteger age = [[person valueForKey:@"_age"]integerValue];
NSLog(@"KVC方式存取：name:%@,age:%ld",name,age); }
@end
如果需要打印输出对象，还需要重写Person类的descaprition方法。
#import "Person.h" @implementation Person
-(NSString *)description
{
return [NSString stringWithFormat:@"name:%@,age:%ld",_name,_age];
}
@end
3、扩展KVC的使用
Book类的.h文件 #import <Foundation/Foundation.h> @interface Book : NSObject
@property(copy,nonatomic)NSString *bookName; @end Book类的.m文件
#import "Book.h" @implementation Book
-(NSString *)description
{
return [NSString stringWithFormat:@"%@",_bookName];
}
@end
Person类的.h文件 #import <Foundation/Foundation.h>
@class Book;
@interface Person : NSObject
@property(copy,nonatomic)NSString *name;
@property(assign,nonatomic)NSInteger age;
@property(strong,nonatomic)Book *book;
@end Person类的.m文件
#import "Person.h" @implementation Person
-(NSString *)description
{
return [NSString stringWithFormat:@"name:%@,age:%ld",_name,_age];
}
@end
最后是实现文件。
#import "ViewController.h"
#import "Book.h"
#import "Person.h"
@interface ViewController () @end
@implementation ViewController - (void)viewDidLoad {
[super viewDidLoad];
Person *p1 = [[Person alloc]init];
[p1 setValue:@"Tom" forKey:@"name"];
[p1 setValue:@ forKey:@"age"];
Book *book1 = [[Book alloc]init];
book1.bookName = @"iPhone";
p1.book = book1; Person *p2 = [[Person alloc]init];
[p2 setValue:@"Jerry" forKey:@"name"];
[p2 setValue:@ forKey:@"age"];
Book *book2 = [[Book alloc]init];
book2.bookName = @"iOS";
p2.book = book2; NSLog(@"%@%@",p1,[p2 valueForKeyPath:@"name"]); NSArray *person = @[p1,p2];
NSLog(@"%@",person); NSArray *arrayM = [person valueForKeyPath:@"book.bookName"];
NSLog(@"%@",arrayM);
} @end
二、KVO机制
1、KVO简述
KVO,即：Key-Value Observing，它提供一种机制，当指定的对象的属性被修改后，则对象就会接受到通知。简单的说就是每次指定的被观察的对象的属性被修改后，KVO就会自动通知相应的观察者了。
2、使用方法
系统框架已经支持KVO，所以在使用的时候非常简单。使用步骤：
（1）注册需要观察的对象的属性addObserver:forKeyPath:options:context:
（2）实现observeValueForKeyPath:ofObject:change:context:方法，这个方法当观察的属性变化时会自动调用
（3）取消注册观察removeObserver:forKeyPath:context:
#import <Foundation/Foundation.h> @interface Person : NSObject
{
NSString *_name;
}
@end
#import "Person.h" @implementation Person
//接受被观察者发生变动后的通知
-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
NSLog(@"%@,%@,%@,%@",keyPath,object,change,context);
}
@end
再添加一个股票类，让Person作为观察者，对股票的价格进行监听。
#import <Foundation/Foundation.h> @interface Stock : NSObject
{
NSString *_name;
float _price;
}
@end
实现文件内容：
#import "ViewController.h"
#import "Person.h"
#import "Stock.h"
@interface ViewController ()
@property(strong,nonatomic)Person *person;
@property(strong,nonatomic)Stock *stock;
@end @implementation ViewController - (void)viewDidLoad {
[super viewDidLoad];
//创建观察者
self.person = [[Person alloc]init];
[self.person setValue:@"Tom" forKey:@"_name"]; //创建股票
self.stock = [[Stock alloc]init];
[self.stock setValue:@"sxt" forKey:@"_name"];
[self.stock setValue:@1.2 forKey:@"_price"]; //设置观察者
[self.stock addObserver:self.person forKeyPath:@"_price" options:NSKeyValueObservingOptionNew |NSKeyValueObservingOptionOld context:@"add"];
}
//单击按钮让股票价格加1
- (IBAction)buttonClicked:(UIButton *)sender
{
float price = [[self.stock valueForKey:@"_price"]floatValue];
[self.stock setValue:@(price+1.0) forKey:@"_price"];
} -(void)dealloc
{
//删除观察者
[self.stock removeObserver:self.person forKeyPath:@"_price"];
}
@end