《More Effective C++》學習心得（八） 要求（或禁止）對象產生於heap中

一。要求對象必須產生於heap中

#include <iostream>
#include <memory>
using   namespace  std; 
class Print
{
public:
	void submitJob()
	{
		cout<<this<<":Print::submitJob()\n";
	}
	void reset()
	{
		cout<<this<<":Print::reset()\n";
	}
	void performSelfTest()
	{
		cout<<"Print::performSelfTest()\n";
	}
	Print()
	{
		cout<<"Print::Print()\n";
	}
	Print(const Print &rhs)
	{
		cout<<"Print::copy Print()\n";
	}
	//pseudo deconstructor
	void desttoy()
	{
		delete this;
	}
protected:
	//將析構函數聲明爲private會影響繼承和內含，所以改爲protected
	~Print()
	{
		cout<<"Print::~Print()\n";
	}
private:


};

int  main() {   
//	Print p;  //it's error,because the deconstructor is private
	Print *p1=new Print();
	//delete p1;  //this's also error,because it attempt to invoke the private deconstrutor
	p1->desttoy();

}

雖然書中說也可以見所有構造函數私有，但明顯沒有將析構函數私有來的簡單，原因：析構函數只有一個，二構造函數五花八門（包括拷貝構造函數）。

同樣，將析構函數私有帶來的致命問題是：妨礙了繼承（inheritance）和內含（containment）。

二。禁止對象產生於heap中

#include <iostream>
#include <memory>
using   namespace  std; 
class Print
{
public:
	void submitJob()
	{
		cout<<this<<":Print::submitJob()\n";
	}
	void reset()
	{
		cout<<this<<":Print::reset()\n";
	}
	void performSelfTest()
	{
		cout<<"Print::performSelfTest()\n";
	}

protected:

private:
	static void *operator new(size_t size);
	static void operator delete(void *ptr);



};

int  main() {   
	Print p1;
	static Print p2;
//	Print *p3=new Print();//it's error

}