compilation firewalls

最新推荐文章于 2024-12-16 12:38:10 发布

yukuaishi

最新推荐文章于 2024-12-16 12:38:10 发布

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分类专栏： Exception C++摘记文章标签： compilation dependencies class interface go up

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探讨C++中使用透明指针隐藏类实现细节的方法，分析不同封装策略的优缺点，包括将私有数据、成员及函数分别放入内部类XImpl中的影响。

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// In C++, when anything in a class definition changes (even private members), 
// all users of that class must be recompiled. To reduce these dependencies, 
// a common technique is to use an opaque pointer to hide some of the implementation details.


class X 
{	
public:
	/* ... public members ... */	
protected:	
	/* ... protected members? ... */	
private:	
	/* ... private members? ... */	
	struct XImpl;	
	XImpl* pimpl_;         // opaque pointer to	
	// forward-declared class	
};

// The questions for you to answer are:
// What should go into XImpl? There are four common disciplines.
// 1.Put all private data (but not functions) into XImpl.
// 2.Put all private members into XImpl.
// 3.Put all private and protected members into XImpl.
// 4.Make XImpl entirely the class that X would have been, 
//   and write X as only the public interface made up entirely of simple forwarding functions (a handle/body variant).
// What are the advantages/drawbacks of each? How would you choose among them?
// Does XImpl require a pointer back to the X object?

// Option 1 (Score: 6 / 10): Put all private data (but not functions) into XImpl. 
// Option 2 (Score: 10 / 10): Put all nonvirtual private members into XImpl. 

// Virtual functions should normally be private,