objective-c中的cocoa特性：KVC-键值编码（转）

#import <Foundation/Foundation.h>  
@interface Human:NSObject  
{  
	NSString *name;  
	int age;  
	Human *child;  
}  
//注意下面并没有写age的property  
@property (copy) NSString *name;  
@property (retain)Human *child;  

@end  

@implementation Human  
  
@synthesize name;  
@synthesize child;  

@end  
  
int main(int argc, const char * argv[])  
{  
  
  @autoreleasepool {  
      
    Human *human = [[Human alloc]init];  
    Human *child=[[Human alloc]init];  
      
    [human setValue:@"holydancer" forKey:@"name"];//将name属性设置为"holydancer"  
    NSString *nameOfHuman=[human valueForKey:@"name"];//将human中的name属性取出  
    NSLog(@"%@",nameOfHuman);  
      
    [human setValue:[NSNumber numberWithInt:20] forKey:@"age"];//将没有set方法的age属性赋值  
    NSLog(@"%@",[human valueForKey:@"age"]);//将没有get方法的age值取出。  
      
    [human setValue:child forKey:@"child"];//等价于human.child=child;  
      
    //将human中的属性child的name属性设置为"dancer's child"          
    [human setValue:@"dancer's child" forKeyPath:@"child.name"];  
    //这里的方法名叫setValue:forKeyPath,可以用来设置当前对象属性的属性。  
      
    //将human中的属性child的age属性取出。          
   NSLog(@"%@",[human valueForKeyPath:@"child.name"]);  
         
  }  
  return 0;  
}   2012-03-20 19:58:30.634 kvc[3197:403] holydancer

#import <Foundation/Foundation.h>  
@interface Human:NSObject  
{  
   		NSString *name;  
	int age;  
	NSMutableArray *children;  
}

//注意下面并没有写age的property  
@property (copy) NSString *name;  
@property (retain)Human *child;  
@end  
	
@implementation Human  
  
@synthesize name;  
@synthesize child;  
@end  
  
int main(int argc, const char * argv[])  
{  
  @autoreleasepool {  
      
    Human *human = [[Human alloc]init];  
    Human *child1=[[Human alloc]init];  
    Human *child2=[[Human alloc]init];  
    [child1 setValue:[NSNumber numberWithInt:5] forKey:@"age"];  
    [child2 setValue:[NSNumber numberWithInt:10] forKey:@"age"];//给两个child的age属性赋值，因为没有property，所以用KVC模式赋值  
    NSMutableArray *children =[[NSMutableArray alloc]init];  
    [children addObject:child1];  
    [children addObject:child2];  
    //上面是为了将两个Human类包装为NSArray，准备放入human类  
    [human setValue:children forKey:@"children"];  
    NSNumber *count=[human valueForKeyPath:@"children.@count"];//利用键路径计算human对象中children属性包含的元素个数  
    NSNumber *sumOfAge=[human valueForKeyPath:@"children.@sum.age"];//计算children中所有对象的年龄和  
    NSNumber *maxOfAge=[human valueForKeyPath:@"children.@max.age"];//计算children中所有对象年龄最大的  
    NSNumber *minOfAge=[human valueForKeyPath:@"children.@min.age"];//计算children中所有对象年龄最小的  
    NSNumber *avgOfAge=[human valueForKeyPath:@"children.@avg.age"];//计算children中所有对象年龄的平均数  
    //@是运算符的  
    NSLog(@"children中有%@个元素，年龄和为%@，最大年龄为%@,最小年龄为%@,平均年龄为%@",count,sumOfAge,maxOfAge,minOfAge,avgOfAge);  
   
  }  
  return 0;  
}