Objective-C中字典类

字典是用于保存具有映射关系(key-value对)的数据集合.一个key-value对认为是一个条目(Entry),字典是存储key-value对的容器.

字典类的特点

与数组不同,字典靠key存取元素;

key值不能重复,value必须是对象;

键值对在字典中是无序存储的.

字典分为不可变字典(NSDictionary)和可变字典(NSMutableDictionary).

不可变字典(NSDictionary)

字典一旦创建,键值对不可更改,不可添加, 不可删除.

仅能读取key或value.

创建字典对象

NSDictionary *dic1 = [NSDictionary dictionaryWithObject:@"张三" forKey:@"name"];
NSLog(@"dic1 %@", dic1);

创建有多个key-value对的字典

NSDictionary *dic2 = [NSDictionary dictionaryWithObjectsAndKeys:@"a", @"1", @"b", @"2", @"c", @"3", nil];
NSLog(@"dic2 %@", dic2);
//获取所有的key
NSLog(@"key %@", dic2.allKeys);
// 获取所有的value
NSLog(@"value %@", dic2.allValues);
// 通过key 找 value
// 根据key获取对应value
NSLog(@"object %@", [dic2 objectForKey:@"2"]);

可变字典(NSMutableDictionary)

创建可变字典

NSMutableDictionary *mDic = [NSMutableDictionary dictionary];
[mDic setObject:@"lilei" forKey:@"name"];
[mDic setObject:@"m" forKey:@"sex"];
NSLog(@"mDic %@", mDic);

添加/修改key-value对

// 当key不存在的时候 添加key-value对
// 当key存在的时候 找到对应的key 替换对应value内容
[mDic setObject:@"lilei" forKey:@"name"];
[mDic setObject:@"male" forKey:@"sex"];
NSLog(@"mDic %@", mDic);
// 修改
[mDic setObject:@"hanmeimei" forKey:@"name"];
NSLog(@"mDic %@", mDic);

删除字典

// 删除
[mDic removeObjectForKey:@"name"];
NSLog(@"mDic %@", mDic);

遍历字典

// 遍历字典
NSDictionary *dic = [NSDictionary dictionaryWithObjectsAndKeys:@"lilei", @"name", @"male", @"sex", @"18", @"age", nil];
NSLog(@"dic %@", dic);
NSArray *arr1 = dic.allKeys;
for (NSInteger i = 0; i < arr1.count; i++) {
// 获取每一个key值
NSString *key = [arr1 objectAtIndex:i];
// 根据key获取对应value
NSLog(@"key: %@, value: %@", key, [dic objectForKey:key]);
}