黑马程序员---OC学习笔记之NSDictionary的介绍及使用

来源：互联网发布：下载windows系统的网站编辑：程序博客网时间：2024/06/02 13:12

——Java培训、Android培训、iOS培训、.Net培训——–

1、NSDictionary介绍

NSDictionary 的作用类似：通过一个key，就能找到对应的value。它是不可变的，一旦初始化完毕，其内容就无法被修改
而且字典是无序的。

2、创建

//NSDictionary介绍与使用        //1）创建字典，一旦创建，内容就不可改变        //空字典        NSDictionary *dic1 = [NSDictionary dictionary];        //2）创建只有一个键值对的字典        NSDictionary *dic2 = [NSDictionary dictionaryWithObject:@"Amos" forKey:@1];        NSLog(@"dic2 = %@",dic2);        //3）创建有多个键值对的字典        //【注意】字典的key和value都必须是OC对象不能是基础数据类型        //方式一：NSDictionary *dic3 = [NSDictionary dictionaryWithObjects:[NSArray arrayWithObjects:@"Amos",@"Allen",@"Andy", nil]forKeys:[NSArray arrayWithObjects:@"1",@"2",@"3", nil]];        //方式二：        NSDictionary *dic3 = [NSDictionary dictionaryWithObjectsAndKeys:@"Amos",@"1",@"Allen",@"2", nil];        NSLog(@"dic1 = %@",dic3);        //4）快速创建字典        //@{key:vaule}        NSDictionary *dic4 = @{@1: @"Amos",@2: @"Allen",@3: @"Andy"};        NSLog(@"dic1 = %@",dic4);

3、字典的特点

1）字典的key是不能重复的，如果重复了将不会被添加到字典
2）键值对存储数据是无序的
3）键值对集合可以根据key快速获取数据

4、基本用法

1）获取地点键值对个数，即字典长度
- (NSUInteger)count;
例如：
NSUInteger count = dic4.count;

2）根据key值去value
NSString *name = [dic4 objectForKey:@1];
NSLog(@”name = %@”,name);

5、字典的遍历

 NSDictionary *dic4 = [NSDictionary dictionaryWithObjectsAndKeys:@"1", @"Amos",@"2", @"Allen",@"3", @"Andy", nil];        //遍历字典        //1）普通方法：先获取key，再根据key获取value        for (NSString *key in dic4) {            NSLog(@"key = %@ value = %@",key,[dic4 objectForKey:key]);        }        //2）block遍历        [dic4 enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {            NSLog(@"key = %@ value = %@",key,obj);        }];

2015-10-08 12:00:53.410 DictionaryDemo[3832:303] key = Amos value = 1
2015-10-08 12:00:53.412 DictionaryDemo[3832:303] key = Allen value = 2
2015-10-08 12:00:53.413 DictionaryDemo[3832:303] key = Andy value = 3
2015-10-08 12:00:53.413 DictionaryDemo[3832:303] key = Amos value = 1
2015-10-08 12:00:53.414 DictionaryDemo[3832:303] key = Allen value = 2
2015-10-08 12:00:53.414 DictionaryDemo[3832:303] key = Andy value = 3

0 0