kvc和字典在创建键值对时的相同与区别(setValue forKey )(setObject forKey)

来源：互联网发布：金10数据网编辑：程序博客网时间：2024/05/05 16:05

首先来定义一个字典

NSMutableDictionary *dic =[NSMutableDictionary dictionaryWithObjectsAndKeys:@"1",@"2",@"3",@"4",@"5",@"6", nil];

[setValue: forKey:]和[setObject: forKey:]相同点

1.当key和value对应的都有值

当key和value都有值时,key所对应的值在字典中不存在时,就可以添加  当key已经存在时,都不会创建键值对  在字典中,value可以重复,但key必须只有一个

        代码段:NSMutableDictionary *dic =[NSMutableDictionary dictionaryWithObjectsAndKeys:@"1",@"2",@"3",@"4",@"5",@"6", nil];        (1)[dic setValue:@"6"forKey:@"7"];     NSLog(@"%@",dic);        (2)[dic setObject:@"6" forKey:@"7"];    NSLog(@"%@",dic);      两种情况结果都是:2015-07-24 20:46:25.860 OC07_类的扩展[1543:105974] {                                        2 = 1;                                        4 = 3;                                        6 = 5;                                        7 = 6; }

2.当key的值为空时

[setValue: forKey:]和[setObject: forKey:]在创建键值对时都会直接崩溃,也就是说在添加键值对时,key必须有对应的值,不能为空

[setValue: forKey:]和[setObject: forKey:]区别

1.kvc中创建键值对用:[setValue: forKey:]

代码段:NSMutableDictionary *dic =[NSMutableDictionary dictionaryWithObjectsAndKeys:@"1",@"2",@"3",@"4",@"5",@"6", nil];    [dic setValue:nil forKey:@"2"];     NSLog(@"%@",dic);    结果: 2015-07-24 20:37:49.603 OC07_类的扩展[1511:103886] {                    4 = 3;                    6 = 5;                    }

在kvc中当 key的值在字典中有相对应的值时,value值为空时,[setValue: forKey:]对应的功能是移除键值对

2.字典中创建键值对用:[setObject: forKey:]

代码段:NSMutableDictionary *dic =[NSMutableDictionary         dictionaryWithObjectsAndKeys:@"1",@"2",@"3",@"4",@"5",@"6", nil];    [dic setObject:nil forKey:@"4"];    NSLog(@"%@",dic);    结果为:崩溃

在用[setObject: forKey:]创建键值对时,key的值在字典中有相对应的值时,value值为空时,整个程序直接崩溃

1 0