EffectiveC++ Item12

看来如果类比较复杂，自己写copying fun还是比较麻烦的事情：

#include <iostream>
#include<string>
using namespace std;

class Widget
{
public:
	Widget(int aData):m_Data(aData)
	{
	}
	virtual void Swap(Widget &aRhs)
	{
		int lTemp = aRhs.m_Data;
		aRhs.SetData(m_Data);
		m_Data = lTemp;
	}
	Widget& operator=(const Widget &aRhs)
	{
		Widget lTemp(aRhs);
		Swap(lTemp);
		return *this;
	}
	virtual int GetData() const
	{
		return m_Data;
	}
	virtual void SetData(int aData)
	{
		m_Data = aData;
	}
private:
	int m_Data;
};
class Drived: public Widget
{
public:
	Drived(int aData):Widget(0),m_DriveData(aData)
	{
	}
	void Swap(Drived &aRhs)
	{
		Widget::Swap(aRhs);
		int lTemp = aRhs.m_DriveData;
		aRhs.SetData(m_DriveData);
		m_DriveData = lTemp;
	}
	Drived(const Drived &aDrived):Widget(aDrived),m_DriveData(aDrived.m_DriveData)
	{
	}
	Drived& operator=(const Drived &aRhs)
	{
		Drived lDrived(aRhs);
		Widget::operator=(lDrived);
		Swap(lDrived);
		return *this;
	}
	virtual int GetData() const
	{
		return m_DriveData;
	}
	virtual void SetData(int aData)
	{
		m_DriveData = aData;
	}
private:
	int m_DriveData;
};

int main()
{
	Widget lTest1(10);
	Widget lTest2(-10);
	lTest2 = lTest1;
	cout << lTest2.GetData() << endl;
	Drived lDrived1(20);
	Drived lDrived2(-20);
	lDrived1 = lDrived2;
	cout << lDrived2.GetData() << endl;
}