C ++：auto_ptr +向前声明？

问题描述

我有这样的类：

class Inner;

class Cont
{
public:
    Cont();
    virtual ~Cont();
private:
    Inner* m_inner;
};

，构造函数创建 Inner 与 new 和析构函数 delete

现在我想更改此代码以使用 auto_ptr ，所以我写：

in the .cpp, the constructor creates an instance of Inner with new and the destructor deletes it. This is working pretty well.
Now I want to change this code to use auto_ptr so I write:

class Inner;

class Cont
{
public:
    Cont();
    virtual ~Cont();
private:
    std::auto_ptr<Inner> m_inner;
};

现在，构造函数初始化了 auto_ptr 析构函数什么也不做。

Now, the constructor initialized the auto_ptr and the destructor does nothing.

但它不工作。当我实例化这个类时，问题似乎出现。我收到此警告：

But it doesn't work. the problem seem to arise when I'm instantiating this class. I get this warning:

好吧，这显然很不好，我明白为什么会发生，编译器不知道当实例化 auto_ptr< Inner>

Well, this is obviously very bad and I understand why it happens, The compiler doesn't know about the d'tor of Inner when instantiating the template of auto_ptr<Inner>

所以我的问题：是否有一种方法使用 auto_ptr 与前向声明，就像我在使用纯平指针的版本中一样？

每个类我声明一个指针是一个巨大的麻烦，有时，只是不可能的 #include

So my question: Is there a way to use auto_ptr with a forward declaration like I did in the version that uses just plain pointers?
Having to #include every class I declare a pointer to is a huge hassle and at times, just impossible. How is this problem usually handled?

推荐答案

您需要包含定义 class Inner 到 Cont ::〜Cont（）实现所在的文件。这种方式你仍然有一个向前的声明，在teh头定义 class Cont ，编译器看到 class Inner 定义，析构函数。

You need to include the header defining class Inner into the file where Cont::~Cont() implementation is located. This way you still have a forward declaration in teh header defining class Cont and the compiler sees class Inner definition and can call the destructor.

//Cont.h
class Inner; // is defined in Inner.h
class Cont
{
    virtual ~Cont();
    std::auto_ptr<Inner> m_inner;
};

// Cont.cpp
#include <Cont.h>
#include <Inner.h>

Cont::~Cont()
{
}

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