KVC

KVC就是 key--value—coding  可以在没有给属性设置property的情况下访问属性。

编写了一个接口 定义了一个有复合属性和基本属性：

#import <Cocoa/Cocoa.h>
#import "Author.h"

@interface Books : NSObject {
    NSString * name;
    Author * author;
    float price;
    NSArray * array;
}
@end

下面是Author接口：

#import <Cocoa/Cocoa.h>

@interface Author : NSObject {
    NSString * name;

}

@end

 

下面是主函数中的内容 ，练习一下KVC是怎样实现的

NSAutoreleasePool * pool =[[NSAutoreleasePool alloc]init];

    Books * book=[[[Books alloc]init]autorelease];
    Author * author=[[[Author alloc]init]autorelease];
    [book setValue:@"Ojbect-C 入门" forKey:@"name"];
    [author setValue:@"hongxing" forKey:@"name"];
    [book setValue:author forKey:@"author"];

    NSLog(@"this is authorname:%@",[author valueForKey:@"name"]);
    NSLog(@"this is bookname:%@",[book valueForKey:@"name"]);
    NSLog(@"this is book.author.name:%@",[book valueForKeyPath:@"author.name"]);

    Books * book1=[[[Books alloc]init]autorelease];
    [book1 setValue:@"4.5" forKey:@"price"];
    [book1 setValue:author forKey:@"author"];
    Books * book2=[[[Books alloc]init]autorelease];
    [book2 setValue:@"5.4" forKey: @"price"];
    NSArray *array=[NSArray arrayWithObjects:book1,book2,nil];
    [book setValue:array forKey:@"array"];

    NSLog(@"books price is:%@",[book valueForKeyPath:@"array.price"]);
    NSLog(@"books price count is:%@",[book valueForKeyPath:@"array.@count.price"]);
    NSLog(@"books price count is:%@",[book valueForKeyPath:@"array.@avg.price"]);
    NSLog(@"books price count is:%@",[book valueForKeyPath:@"array.@max.price"]);
    NSLog(@"books price count is:%@",[book valueForKeyPath:@"array.@min.price"]);
    NSLog(@"books price count is:%@",[book valueForKeyPath:@"array.@sum.price"]);
    NSLog(@"books price count is:%@",[book valueForKeyPath:@"array.author.name"]);
    [pool drain];