OC中KVC设计模式简单实用<代码演示>

#import <Foundation/Foundation.h>
//作者对象类
@interface Author : NSObject

{

    @private

    NSString *_authorName;

}

@end

//书籍对象类
#import "Author.h"
//KVC--key-value-coding的使用
@interface BookKVC : NSObject

{

@private

    //通常变量设置为私有后，在没有访问器和设置的情况下可以使用KVC

    //变量为public 时可以使用对象指针访问Book->_bookName

    NSString *_booKName;//书籍名称

    NSInteger _price;//书的价格

    Author *_author;//作者对象

    NSArray *_relativeBooks;//相关书籍

}

@end

    //kvc模式下可以带“_author”也直接是“author”

    BookKVC *book = [[BookKVC alloc] init];

    //public情况下
//    book->_booKName = @"public containt";
//    [book setValue:@"this is KVC layoutModel" forKey:@"booKName"];
//    NSString *name = [book valueForKey:@"booKName"];

    

    /*键值访问*/

    [book setValue:@"this is KVC layoutModel" forKey:@"_booKName"];

    NSString *name = [book valueForKey:@"_booKName"];

    NSLog(@"%@",name);

    //通过路径查找

    Author *author = [[Author alloc] init];

    [author setValue:@"this is authorKVC" forKey:@"_authorName"];

    

    /*路径访问*/

    //设置书籍中的作者对象

    [book setValue:author forKey:@"_author"];

    //通过路径获取

    NSString *authorName = [book valueForKeyPath:@"_author._authorName"];

    NSLog(@"%@",authorName);

    //也可以通过路径访问重新设置其属性

    [book setValue:@"this is reSetName by path" forKeyPath:@"_author.authorName"];

    NSString *newName = [book valueForKeyPath:@"author.authorName"];

    NSLog(@"%@",newName);

    

    /*一对多访问*/

    NSMutableArray *relateBook = [NSMutableArray arrayWithCapacity:3];

    for (int i
= 0 ; i < 3;
i++) {

        BookKVC *oneMore = [[BookKVC alloc] init];

        NSString *names = [NSString stringWithFormat:@"hong%d",i];

        NSInteger price = i+5;//书的价格

        [oneMore setValue:names forKey:@"_booKName"];//设置书名

        [oneMore setValue:[NSNumber numberWithInt:price] forKey:@"_price"];//设置书的价格

        [relateBook addObject:oneMore];

        RELEASE_SAFETY(oneMore);

    }

    //设置书籍对象的_relativeBooks

    [book setValue:relateBook forKey:@"_relativeBooks"];

    //获取存入的数组对象

    NSArray *getNames = [book valueForKeyPath:@"_relativeBooks._booKName"];

    NSLog(@"%@",getNames);

    

    

    

    /*KVC的一些加点运算语法 @sum
@min @max @avg @count等*/

    //数组中数的数量

    NSString *count = [book valueForKeyPath:@"_relativeBooks.@count"];

    NSLog(@"%@",count);

    //数组中书本的价格最大值

    NSString *max = [book valueForKeyPath:@"_relativeBooks.@max._price"];

    NSLog(@"%@",max);

    //数组书籍的价格的最小值

    NSString *min = [book valueForKeyPath:@"_relativeBooks.@min._price"];

    NSLog(@"%@",min);

    //数组中书籍价格的平均值

    NSString *avg = [book valueForKeyPath:@"_relativeBooks.@avg._price"];

    NSLog(@"%@",avg);

    //安全释放

    RELEASE_SAFETY(book);

    RELEASE_SAFETY(author);