获取参数类型，模板，C ++ [英] Get type of the parameter, templates, C++

问题描述

有以下简化的数据结构：

There is the following simplified data structure:

Object1.h

Object1.h

template <class T>
class Object1
{
  private:
     T a1;
     T a2;
  public:
     T getA1() {return a1;}
};

Object2.h

Object2.h

template <class T>
class Object2: public Object1 <T>
{
   private:
      T b1;
      T b2;
  public:
     T getB1() {return b1;}
}

有什么方法如何在下面的函数中获取对象的类型T：

Is there any way how to get type T of an object in the folowing function:

Functions.h

Functions.h

template <class Object>
void (Object *o1, Object *o2)
{
   T = o1.getA1();  //Is it possible to get T from object o1?
   ...
}

或者我们必须提供有关数据的附加信息两个对象的类型：

or we must give an additional information about data types of both objects:

template <class T, class Object>
void (Object *o1, Object *o2)
{
   T = o1.getA1();
   ...
}

推荐答案

添加typedef：

template <class T>
class Object1
{
  private:
     T a1;
     T a2;
  public:
     T getA1() {return a1;}
     typedef T type;
};

template <class Object>
void foo(Object *o1, Object *o2)
{
   typename Object::type x = o1.getA1();
   ...
}

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