在C ++中使用包含不同类型键的映射 [英] Have a map with keys consisting of different types in C++

问题描述

我目前在C ++中使用地图，并且有一些int和布尔值的值，尽管其中大部分都是字符串。我知道在Java中我可以这样做：

I currently am using a map in C++ and have a couple of values that are ints and booleans, though the majority of them are strings. I know in Java I could do something like this:

std::map<string, Object*> mapvar;

但是在C ++中有一个 Object 等价物??如果没有，我有什么办法可以正确地让值为 std :: string ， int 或 bool ？

but is there an Object equivalent in C++?? If not, is there any way I could properly have values being a std::string, int, or bool?

推荐答案

我不知道你可以拥有一个方法 std :: map ，其中可以使用 stdlib 开启多个类型的键。

I don't know of a way you could have a std::map with keys that can be multiple types using the stdlib out of the box.

Boost有一个变体类型，其功能或多或少像您想要的那样。

Boost has a variant type that functions more or less like what you want.

typedef boost::variant<std::string, int, bool> key_type;
std::map<key_type, Object*> mapvar

此地图只接受在您选择的key_type中定义的键 ，所以你也不能使用 std :: wstring 作为关键字而不显式声明它。这将是在任何之上使用变体的优点。后者可能会喜欢吃任何你发送的类型，而前者会给你一个编译时错误。

This map will only accept keys that are defined in your chosen key_type, so you could not also use, say, a std::wstring as a key without explicitly declaring it. This would be the advantage of using a variant over any. The latter might happily eat whatever type you send its way, while the former will give you a compile time error.

如果你打算使用 boost :: variant 作为你的密钥，那么你需要阅读boost文档，并研究构建变体对象以及是否涉及他们有排序预定义。 std :: map 建立在运算符< 之上（除非您在其他排序函子上模板化）需要确保您的变体类型的工作定义由库或您自己提供。

If you are going to use a boost::variant as your key then you need to read the boost documentation and look into what is involved in constructing variant objects and whether or not they have sorting pre-defined. std::map is built on operator< (unless you template it on some other sorting functor) so you'll need to make sure a working definition for your variant type is provided by either the library or yourself.

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为什么你想要这样的地图呢？

Why do you want to have such a map in the first place?

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