Saving a variable temporarily

// temp.h : header file for CTemp class
// Created by: Alvaro Mendez - 10/20/1999

#ifndef __TEMP_H__
#define __TEMP_H__


///////////////////////////////////////////////////////////////////////////////
// Variable-value saver class

// Class CTemp has a template constructor which allows you to save a 
// variable's current value (on construction) so that it can be restored 
// at a later time (on destruction).
//
// Sample usage:  CTemp v = variable_whose_value_you_are_saving;
//
class CTemp
{
public:
	// Base class for template class below.
	class SaverBase
	{
	public:
		virtual ~SaverBase() { }
		virtual void Restore() = 0;
	};

	// Template class which saves the value in construction
	// and restores it on destruction.
	template <class T>
	class Saver : public SaverBase
	{
	public:
		Saver(T& valueToSave) :
			m_ref(valueToSave),
			m_val(valueToSave)
		{ }

		virtual ~Saver()
		{
			Restore();
		}

		virtual void Restore()
		{
			m_ref = m_val;
		}

	private:
		T& m_ref;
		T m_val;
	};

public:
	template <class T> 
	CTemp(T& valueToSave) :
		m_pVar(new Saver<T>(valueToSave))
	{ }

	~CTemp()
	{
		Restore();
		delete m_pVar;
	}

	void Restore()
	{
		m_pVar->Restore();
	}

private:
	// Prevent accidental self copying
	CTemp(const CTemp&);
	CTemp& operator=(const CTemp&);  

protected:
	SaverBase* m_pVar;
};

#endif	// __TEMP_H__