void initializeGui() and void setGuiScreen(string gui)

string actualGui = "";

void initializeGui()
{
    guiMainMenu = GuiMainMenu();
    guiMainMenuPtr = &guiMainMenu;

    guiGame = GuiGame();
    guiGamePtr = &guiGame;

    setGuiScreen("GuiMainMenu");
}

void setGuiScreen(string gui)
{
    actualGui = gui;
    if(actualGui == "GuiGame")
        guiScreenPtr = guiGamePtr;
    else if(actualGui == "GuiMainMenu")
        guiScreenPtr = guiMainMenuPtr;
}