object-c之kvc kvo（人中有属性数组、Book对象，数组中装载Book对象）

KVC(KeyValueCoding)　“键-值-编码”是一种可以直接通过字符串的名字（key）来访问类实例变量的机制。
KVC可以用来访问和设置实例变量的值。
设置方式：[self setValue:aName forKey:@"name"]

　　　　　[self setValue:aName forKeyPath:@"person.name"]

访问方式： aString　=　[self valueForKey:@"name"]
　　　　　aString　=　[self valueForKeyPath:@"person.name"]

主函数内容
        Person *xiaoLi = [[Person alloc]init];
        //        Book *book = [[Book alloc]init];
        //        [book addMyObserver];
        
        [xiaoLi setBookName:@"《红楼梦》" andPrice:58];
        [xiaoLi setBookName:@"《三国演义》" andPrice:56.5];
        [xiaoLi setBookName:@"《水浒传》" andPrice:68.8];
        [xiaoLi setBookName:@"《西游记》" andPrice:75.2];
        
        NSArray *array = [xiaoLi valueForKeyPath:@"bookArray"];
        
        for (Book *book in array)
        {
            
            NSLog(@"%@ %@",[book valueForKey:@"bookName"],[book valueForKey:@"price"]);
        }



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

@interface Person : NSObject
{
    NSString *name;
    NSMutableArray *bookArray;
    Book *aBook;
}

- (void)setBookName:(NSString *)bookName andPrice:(float)price;

@end




#import "Person.h"
#import "Book.h"

@implementation Person

- (void)setBookName:(NSString *)bookName andPrice:(float)price
{
    // 如果bookArrar没有初始化，初始化
    if (!bookArray) {
        bookArray = [[NSMutableArray alloc]init];
    }
    
    Book *book = [[Book alloc]init];
    
    // 开始监听书名的变化
    [book addMyObserver];
    
    [self setValue:book forKey:@"aBook"];
    [self setValue:bookName forKeyPath:@"aBook.bookName"];
    
    // 把price封装成NSNumber数据赋值给bookName，读取bookName时会自动转为float
    NSNumber *price1 = [NSNumber numberWithFloat:price];
    [self setValue:price1 forKeyPath:@"aBook.price"];
    
    // 把书装入数组
    [bookArray addObject:aBook];

}

@end




#import <Foundation/Foundation.h>

@interface Book : NSObject

{
    NSString *bookName;
    float price;
}

- (void)addMyObserver;

@end




#import "Book.h"

@implementation Book

- (void)addMyObserver
{
    // 注册监听对象
    [self addObserver:self forKeyPath:@"bookName" options:NSKeyValueObservingOptionNew context:nil];
    //observer
}

    // 监听属性实例值的变化
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    NSLog(@"bookName%@",change);
}

- (void)dealloc
{
    // 移除监听
    [self removeObserver:self forKeyPath:@"bookName"];
    [super dealloc];
}


@end