1、Objective-C

// 1.方法一（不可变字典）
        NSDictionary *dic = [[NSDictionary alloc]initWithObjectsAndKeys:@"a",@"1",@"b",@"2", nil];
        NSLog(@"%@",dic);
//2.方法二（不可变字典）
      NSDictionary *dic01 = [NSDictionary dictionaryWithObjectsAndKeys:@"a",@"1",@"b",@"2",@"c",@"3", nil];
        NSLog(@"%@",dic01);

//可变字典初始化
        NSMutableDictionary *dic03 = [[NSMutableDictionary alloc]initWithObjectsAndKeys:@"1",@"a",@"2",@"b",@"3",@"c", nil];
        NSLog(@"dic03 = %@",dic03);
 
       //增加键值对
        [dic03 setValue:@"4" forKey:@"d"];
        NSLog(@"%@",dic03);
        
        //删除键值对
        [dic03 removeObjectForKey:@"d"];
         NSLog(@"%@",dic03);
        
        //修改value的值
        [dic03 setObject:@"2" forKey:@"a"];
         NSLog(@"%@",dic03);

2、swift

//空字典创建
var someDict = [Int: String]()

//非空字典创建
var dic:[String:String] = ["a":"1","b":"2","c":"3"]

//添加数据(updateValue(forKey:) 增加或更新字典的内容。如果 key 不存在，则添加值，如果存在则修改 key 对应的值)
dic.updateValue("4", forKey: "d")

//修改
dic.updateValue("5", forKey: "d")

//删除数据(removeValueForKey() 方法来移除字典 key-value 对。如果 key 存在该方法返回移除的值，如果不存在返回 nil )
dic.removeValue(forKey: "d")

print( "dic = \(dic), str = \(str)" )