Sorry your browser is not supported!

class Tool {
private:
public:
	void PrimaryTrigger ( );
} myTool;

class SuperSuckyTool {
private:
	bool Selected;
public:
	void PrimaryAction ( );
};

class SuperAwesomeTool {
private:
	bool Selected;
public:
	void PrimaryAction ( );
};

#include <iostream>

// Forward declarations of the derived classes
class SuperSuckyTool;
class SuperAwesomeTool;

class Tool
{
private:
    // Private constructor, so can only be constructed by itself, or by a friend
    Tool() { }


    // The variable must be in the base class - there are no virtual variables
    bool Selected;
    virtual void PrimaryAction ( ) { };


public:

    void Select()   { Selected = true; }
    void Unselect() { Selected = false; }

    virtual void PrimaryTrigger ( )
    {
        std::cout << "Called PrimaryTrigger\n";

        if (Selected)
            PrimaryAction();

        std::cout << "Leaving PrimaryTrigger\n";
    }

    // Almost every inherited class should have a virtual destructor 
    virtual ~Tool() { }

    // Call this to access the only instance of Tool
    static Tool& GetTool()
    {
        static Tool t;      // This is the only instance of the Tool class
        return t;           // And it's returned by reference
    }

    // Make the derived classes friends, otherwise they won't be constructable
    friend class SuperSuckyTool;
    friend class SuperAwesomeTool;

};


class SuperSuckyTool : public Tool
{
public:

    virtual void PrimaryAction ( ) { std::cout << "SuperSuckyTool\n"; }

};


class SuperAwesomeTool : public Tool
{
public:

    virtual void PrimaryAction ( ) { std::cout << "SuperAwesomeTool\n"; }

};


int main()
{

    Tool *SST = new SuperSuckyTool;
    SST->Select();
    SST->PrimaryTrigger();
    delete SST;

    Tool *SAT = new SuperAwesomeTool;
    SAT->Select();
    SAT->PrimaryTrigger();
    delete SAT;

    // Cannot do either of these:
    // Tool *T   = new Tool;
    // Tool T;

    // Can access the 'Tool' single instance like this:
    Tool::GetTool().PrimaryTrigger();

    // Or bind it to a reference and access it like this:
    Tool &ToolRef = Tool::GetTool();
    ToolRef.PrimaryTrigger();
}