找出类及其子里面的类类型 [英] find out the class type inside the class and its children

问题描述

可以说我有类

template<typename PointT>
class Parent {
  public:
  typedef boost::shared_ptr<Parent<PointT> > Ptr;

  inline Ptr
  makeShared ()
  {
    return Ptr (new Parent<PointT> (*this));
  }
};

template<typename PointT>
class Child : public Parent {
  public:
    typedef boost::shared_ptr<Child<PointT> > Ptr;
};

现在想什么，我重写PTR和makeShared（）的定义是通用的，这样从子类（ES）的情况下调用makeShared（）会产生一个指向子类而不是父

Now what I'd like to rewrite the definition of Ptr and makeShared() to be generic, so that calling makeShared() from child class(es) instances would yield a pointer to the child class not the parent

要更清楚调用任何类继承父makeShared（）会给一个指向继承类的一个实例。并呼吁使共享（）的父类将使一个指向父类的一个实例
任何想法？

To make it more clear calling makeShared() on any class inheriting Parent would give a pointer to an instance of that inheriting class. and calling make shared() on the parent class would give a pointer to an instance of Parent class Any ideas?

推荐答案

CRTP将在这里工作：

CRTP will work here:

template<typename Child>
class Parent {
  public:
  typedef boost::shared_ptr<Child> Ptr;

  inline Ptr
  makeShared ()
  {
    return Ptr (new Child(*static_cast<Child *>(this)));
  }
};

template<typename PointT>
class Child : public Parent<Child> {
};

注意 makeShared 是因为它可以用的​​ shared_from_this （在C ++ 11和Boost）。为你的方法更典型的名称是克隆。

Note that makeShared is a fairly confusing name as it could be confused with shared_from_this (in C++11 and Boost). A more typical name for your method is clone.

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