boost::ptr_vector 和 boost::any 的问题

发布于 2024-07-22 07:11:21 字数 1039 浏览 22 评论 0原文

好吧，所以我有一个疑问，我想知道这是否可能：

我正在使用一个数据库，其中包含通用数据（字符串、整数、布尔值等）。每当构造一个对象或修改对象的成员时，我都必须使用特定操作（SELECT 或 UPDATE）查询数据库。首先，这不是一个与数据库相关的问题，我真正的问题是我有一个 ptr_vector ，它保存 boost::any 指向对象成员的指针。在类似这样的代码中：

class Enemy{
  private:
    //some private data...
  public:
    auto_ptr<int> ID_Enemy;
    auto_ptr<string> Enemy_Name;
    //miscellaneous methods...
};

然后我将要修改的成员传递给另一个杂项类的函数，该函数以 boost::any* 作为参数：

misc_class.addValues((boost::any*)(ID_Enemy.get()));
misc_class.addValues((boost::any*)(Enemy_Name.get()));

同一个类接受 any*，并执行以下操作：

auto_ptr<boost::any> val2(val); //being val, the passed any*
Enemy_Values.push_back(val2);

Enemy_Values 是 ptr_vector 。因此，当我访问这个以 Enemy_Values 作为成员的 Misc_class 时，我想更改内部 auto_ptr 指向的值：

misc_class.Enemy_Values[0] = (boost::any)(69);

在这里，我收到一个违规错误。我尝试了很多事情，有人告诉我，我不应该使用 auto_ptr 容器或使用 boost::any 来回转换。我这样做可能吗，还是有更好、更直观的方法？

提前致谢。

原文

ok, so I got a doubt, I want to know if this is possible:

I'm using a database, with generic data (strings, ints, bools, etc...). Whenever an object is constructed or a member of an object is modified, I have to query the database with the specific action (SELECT or UPDATE).
First of all, this isn't a DB related question, my real problem is that I have a ptr_vector which holds boost::any's pointers to members of the object. In code something like this:

class Enemy{
  private:
    //some private data...
  public:
    auto_ptr<int> ID_Enemy;
    auto_ptr<string> Enemy_Name;
    //miscellaneous methods...
};

then I pass the members I want to modify to a function of another miscellaneous class which takes as argument a boost::any*:

misc_class.addValues((boost::any*)(ID_Enemy.get()));
misc_class.addValues((boost::any*)(Enemy_Name.get()));

that same class accepts the any*, and does the following:

auto_ptr<boost::any> val2(val); //being val, the passed any*
Enemy_Values.push_back(val2);

Enemy_Values is a ptr_vector. So when I access this misc_class which has Enemy_Values as member, I want to change the value to which an auto_ptr inside is pointing:

misc_class.Enemy_Values[0] = (boost::any)(69);

And here, I get a violation error. I've tried many things, and someone told me that I shouldn't be using containers of auto_ptr or converting back and forth with boost::any. Is this that I am doing possible, or there is a better and more intuitive way?

Thanks in advance.

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苦笑流年记忆 2024-07-29 07:11:21

(boost::any*)(ID_Enemy.get()) 执行 reinterpret_cast 因为您正在转换不相关的指针类型。这意味着您会得到一个指向 any 的无效指针，它指向真正的整数。
相反，构造一个临时的 boost::any 对象并通过引用将其传递给 addValues：

misc_class.addValues(boost::any(ID_Enemy.get());

您对 auto_ptr 的使用实际上是不正确的：auto_ptr 删除了 freestore 上的对象，但在这里我们而是与当地人打交道。 addValues 只需要将 any 对象的值推入向量：

Enemy_Values.push_back(val);

...而 Enemy_Values 应该只是一个 std::vector。

您可以使用 ptr_vector 和 freestore 分配的 boost::any 对象来完成此操作，但这会比必要的更复杂。

(boost::any*)(ID_Enemy.get()) performs a reinterpret_cast since you are casting unrelated pointer types. This means you get an invalid pointer to an any, pointing to what is really an integer.
Instead, construct a temporary boost::any object and pass it by reference to addValues:

misc_class.addValues(boost::any(ID_Enemy.get());

Your use of auto_ptr is in fact incorrect: auto_ptr deletes objects on the freestore but here we're dealing with locals instead. addValues merely needs to push the value of the any object into the vector: