如何在C ++中构建一个非静态入口点？

Question

I'm trying to initialize my game engine from my main entry point, RPG.cpp. This is what it includes:

#include "stdafx.h"
#include "Engine.h"


int _tmain(int argc, _TCHAR* argv[])
{
    Engine::Go();
    return 0;
}

Engine:Go() is a public method that starts up the game engine. However, it is underlined with the following error: "Error: a nonstatic member reference must be relative to a specific object"

Going through my engine class and making literally everything in it static fixes the problem, but that is a problem in itself. How do I get around this error and not use the keyword static?

Answer 1

Make an instance of Engine and call Go() on it.

Engine e;
e.Go();

static functions are basically free functions that have access to private static members of the class they belong to. By "free function" I mean that they do not belong to an instance, and basically behave like normal C functions (except for their special access privileges).

non- static functions must be called on an instance of the class they belong to.

class Klass {
    int i;
    static int s_i;
public:
    static void static_func() {
        // called without an instance of Klass
        // s_i is available because it is static
        // i is not available here because it is non-static
        // (belongs to an instance of Klass)
    }
    void non_static_func() {
        // called on an instance of Klass
        // s_i is available here because non_static_func() is a member of Klass
        // i is also available here because non_static_func() is called on
        // an instance (k) of Klass
    }
};
void free_func() {
    // s_i and i are both unavailable here because free_func()
    // is outside of Klass
}

int main() {
    // Klass::static_func() is called without an instance,
    // but with the name qualifier Klass:

    Klass::static_func();

    // Klass::non_static_func() is called with an instance:     

    Klass k;
    k.non_static_func();

    // free_func() is called without any instance, and without a name qualifier:

    free_func();
}

Answer 2

You have to actually create an instance of the Engine class.

For example:

Engine e;
e.Go();

Answer 3

You probably want non-static member functions and...

Engine engine;
engine.Go();

static member functions don't need to be invoked on a specific object instance, but then they won't have an implicit this pointer or non- static member variables to access - they can only access other static members of the class.