Objective-C语法之NSDictionary和NSMutableDictionary

Java有Map，可以把数据以键值对的形式储存起来，取值的时候通过key就可以直接拿到对应的值，方便快捷。在Objective-C语言中，词典就是做这样的事情的，和NSArray一样，一个词典对象也能保存不同类型的值，词典也分别有不可变词典和可变的词典（NSDictionary与NSMutableDictionary），前者是线程安全的，后者不是 。

1、不可变词典NSDictionary的主要用法：

[NSDictionary dictionaryWithObjectsAndKeys:..] : 使用键值对直接创建词典对象，结尾必需使用nil标志结束。

[dictionary count]: 得到词典的键值对数量。
[dictionary keyEnumerator]: 将词典的所有key储存在NSEnumerator中，类似于Java语言中的迭代器
[dictionary objectEnumerator]: 将词典的所有value储存在NSEnumerator中
[dictionary objectForKey:key]: 通过传入key对象可以拿到当前key对应储存的值。

代码示例：

?

1. int?main(int?argc,?const?char?*?argv[])??
2. {??
3. ????@autoreleasepool?{??
4. ????????NSDictionary?*dictionary?=?[NSDictionary?dictionaryWithObjectsAndKeys:@"25",@"age",@"张三",@"name",@"男",@"性别",nil];??
5. ????????NSLog(@"%lu",?[dictionary?count]);??
6. ????????NSEnumerator?*enumeratorKey?=?[dictionary?keyEnumerator];??
7. ????????for?(NSObject?*object?in?enumeratorKey)?{??
8. ????????????NSLog(@"key:%@",?object);??
9. ????????}??
10. ??????????
11. ????????NSEnumerator?*enumeratorObject?=?[dictionary?objectEnumerator];??
12. ????????for?(NSObject?*object?in?enumeratorObject)?{??
13. ????????????NSLog(@"value:%@",?object);??
14. ????????}??
15. ????????NSLog(@"key?name的值是:%@",?[dictionary?objectForKey:@"name"]);??
16. ??????????
17. ????}??
18. ????return?0;??
19. }??

打印结果；

[cpp]?view plaincopy
int?main(int?argc,?const?char?*?argv[])??
{??
????@autoreleasepool?{??
????????NSMutableDictionary?*dictionary?=?[NSMutableDictionary?dictionaryWithObjectsAndKeys:@"25",@"age",@"张三",@"name",@"男",@"性别",nil];??
????????[dictionary?setObject:@"30名"?forKey:@"名次"];??
??????????
????????NSLog(@"%lu",?[dictionary?count]);??
????????NSEnumerator?*enumeratorKey?=?[dictionary?keyEnumerator];??
????????for?(NSObject?*object?in?enumeratorKey)?{??
????????????NSLog(@"key:%@",?object);??
????????}??
??????????
????????NSEnumerator?*enumeratorObject?=?[dictionary?objectEnumerator];??
????????for?(NSObject?*object?in?enumeratorObject)?{??
????????????NSLog(@"value:%@",?object);??
????????}??
????????NSLog(@"key?名次的值是:%@",?[dictionary?objectForKey:@"名次"]);??
????????[dictionary?removeObjectForKey:@"名词"];??
????????NSLog(@"%lu",?[dictionary?count]);??
????}??
????return?0;??
}??
?
打印结果：
?
2012-07-09 16:37:07.037 objectiveC[3053:403] 42012-07-09 16:37:07.042 objectiveC[3053:403] key:age2012-07-09 16:37:07.043 objectiveC[3053:403] key:性别2012-07-09 16:37:07.043 objectiveC[3053:403] key:name2012-07-09 16:37:07.044 objectiveC[3053:403] key:名次2012-07-09 16:37:07.044 objectiveC[3053:403] value:252012-07-09 16:37:07.045 objectiveC[3053:403] value:男2012-07-09 16:37:07.045 objectiveC[3053:403] value:张三2012-07-09 16:37:07.046 objectiveC[3053:403] value:30名2012-07-09 16:37:07.046 objectiveC[3053:403] key 名次的值是:30名
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