CODEWITHSUNDEEP
c++
snzm
snzm

Reputation: 159

C++ equivalent of C# object keyword

What is the C++ equivalent of C# object type?

I want to do the C++ equivalent of this:

public enum TokenType {
    Number,
    Operator,
}

public class Token
{
   TokenType type;
   object value;
   public Token(TokenType type, object value)
   {
       switch (type)
       {
           case TokenType.Number:
                break;
           case TokenType.Operator:
               break;
           default:
                // throw some error
                break;
       }
       this.type = type;
       this.value = value;
   }
}

I cannot use a template argument for the class because I do not know if the input is going to be a char, double or string, and I need to declare a Token before knowing.

Upvotes: 0

Views: 1053

Answers (2)

Prodigle
Prodigle

Reputation: 1797

You would need a lot of casting in there but a void* in C++ represents a pointer to Anything. Think of it as a general data store, no length attached to it or anything, just a position.

Depending on what else you need to do it might come in handy.

You can use some try{} wrapped casts to see if it is one of your accepted types

Upvotes: 1

NathanOliver
NathanOliver

Reputation: 180935

Unlike C#, C++ does not have a total type hierarchy. There is no base type int and std::string share. In fact int doesn't even have a base type, it is a fundamental type (built in) and is not a class type.

This means you have to great lengths to achieve something like the C# code. If you know that the types will be limited to some set of types then you can use a std::variant. If you don't have any such limitations then you have to use a std::any. std::variant is like/is a tagged union where std::any utilizes type erasure to store any object inside it. You can then use the visitor pattern to modify the object stored in the variant/any. Since std::variant has a known set of types it gives you more ways to access they type stored in it.

Upvotes: 2

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