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"]

  1 主函数内容
  2         Person *xiaoLi = [[Person alloc]init];
  3         //        Book *book = [[Book alloc]init];
  4         //        [book addMyObserver];
  5         
  6         [xiaoLi setBookName:@"《红楼梦》" andPrice:58];
  7         [xiaoLi setBookName:@"《三国演义》" andPrice:56.5];
  8         [xiaoLi setBookName:@"《水浒传》" andPrice:68.8];
  9         [xiaoLi setBookName:@"《西游记》" andPrice:75.2];
 10         
 11         NSArray *array = [xiaoLi valueForKeyPath:@"bookArray"];
 12         
 13         for (Book *book in array)
 14         {
 15             
 16             NSLog(@"%@ %@",[book valueForKey:@"bookName"],[book valueForKey:@"price"]);
 17         }
 18 
 19 
 20 
 21 #import <Foundation/Foundation.h>
 22 #import "Book.h"
 23 
 24 @interface Person : NSObject
 25 {
 26     NSString *name;
 27     NSMutableArray *bookArray;
 28     Book *aBook;
 29 }
 30 
 31 - (void)setBookName:(NSString *)bookName andPrice:(float)price;
 32 
 33 @end
 34 
 35 
 36 
 37 
 38 #import "Person.h"
 39 #import "Book.h"
 40 
 41 @implementation Person
 42 
 43 - (void)setBookName:(NSString *)bookName andPrice:(float)price
 44 {
 45     // 如果bookArrar没有初始化，初始化
 46     if (!bookArray) {
 47         bookArray = [[NSMutableArray alloc]init];
 48     }
 49     
 50     Book *book = [[Book alloc]init];
 51     
 52     // 开始监听书名的变化
 53     [book addMyObserver];
 54     
 55     [self setValue:book forKey:@"aBook"];
 56     [self setValue:bookName forKeyPath:@"aBook.bookName"];
 57     
 58     // 把price封装成NSNumber数据赋值给bookName，读取bookName时会自动转为float
 59     NSNumber *price1 = [NSNumber numberWithFloat:price];
 60     [self setValue:price1 forKeyPath:@"aBook.price"];
 61     
 62     // 把书装入数组
 63     [bookArray addObject:aBook];
 64 
 65 }
 66 
 67 @end
 68 
 69 
 70 
 71 
 72 #import <Foundation/Foundation.h>
 73 
 74 @interface Book : NSObject
 75 
 76 {
 77     NSString *bookName;
 78     float price;
 79 }
 80 
 81 - (void)addMyObserver;
 82 
 83 @end
 84 
 85 
 86 
 87 
 88 #import "Book.h"
 89 
 90 @implementation Book
 91 
 92 - (void)addMyObserver
 93 {
 94     // 注册监听对象
 95     [self addObserver:self forKeyPath:@"bookName" options:NSKeyValueObservingOptionNew context:nil];
 96     //observer
 97 }
 98 
 99     // 监听属性实例值的变化
100 - (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
101 {
102     NSLog(@"bookName%@",change);
103 }
104 
105 - (void)dealloc
106 {
107     // 移除监听
108     [self removeObserver:self forKeyPath:@"bookName"];
109     [super dealloc];
110 }
111 
112 
113 @end