Question

class A{
private:
     std::string id;
public:
     void f();
};

gives compile time error. However, if I include <string> at top, it compiles correctly. I don’t want to use include statements in headers,though. How can i do it?

Answer 1

You must include <string> in this case to be able to use std::string.

The only moment when you can avoid #including a header is when you’re only using references or pointers of the object in your header. In this case you can use forward declaration. But since std::string is a typedef, you can’t forward declare it, you have to include it.

I’m sure you’re trying to follow the advice to try to #include as less as possible, but you can’t follow it in this case.