NSDictionary NSMutableDictionary的相关API总结_nsmutabledictionary api-优快云博客

本文详细介绍了字典的概念及其在编程中的使用方法，包括创建字典、计算元素个数、获取所有键和值、字典遍历、创建可变字典、添加元素、修改值和移除元素等操作。通过实例演示了如何在实际编程场景中灵活运用字典。

        //字典:用来存储具有一一对应关系的数据.
        //一个key对应一个value key起到了唯一标识作用, key必须是唯一的, 但是一个value可以对应多个key
        //存储的对象是无序的, 一对键值对组成了字典中的一个元素
        //NSDictionary
        /*
        //1.创建对象
        NSDictionary * dic = [[NSDictionary alloc] initWithObjectsAndKeys:@"lili", @"name", @"18", @"age", @"6222222", @"phone", @"男", @"sex", nil];
        NSLog(@"%@", dic);
        NSDictionary * dic1 = [NSDictionary dictionaryWithObjectsAndKeys:@"放弃", @"abandon",@"一个", @"a", @"下标", @"index", nil];
        NSLog(@"%@", dic1);
        //2.求字典的元素个数
        NSInteger count0 = [dic count];
        NSInteger count1 = [dic1 count];
        NSLog(@"%lu", count0);
        NSLog(@"%lu", count1);
        //3.获取所有的key
        NSArray * keys = [dic allKeys];
        NSLog(@"%@", keys);
        //4.根据key获取对应的value
        NSString * value = [dic objectForKey:@"name"];
        NSLog(@"value = %@", value);
        //5.字典遍历
        //字典遍历获得到key 然后根据key在获得相应的value
        for (NSString * key in dic) {
            NSString * value1 = [dic objectForKey:key];
            NSLog(@"!!!!!value1 = %@", value1);
        }
        //NSMutableDictionary
        //1.创建可变字典
        NSMutableDictionary * mDic = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"lili", @"name", @"18", @"age", @"6222222", @"phone", @"男", @"sex", nil];
        //2.往字典中添加元素
        [mDic setObject:@"25" forKey:@"number"];
        NSLog(@"%@", mDic);
        //3.修改key对应的value
        [mDic setObject:@"22" forKey:@"age"];
        NSLog(@"3333%@", mDic);
        //4.移除
        [mDic removeObjectForKey:@"phone"];
        NSLog(@"4444%@", mDic);