C++ 所有者类和子类的派生类

Question

所以假设我有一个由动物园类管理的动物类。

Animal is an abstract class to be derived by other real animal classes
class Animal{
public:
  Animal();
  virtual ~Animal() = 0;
  //Various animal related functions
}

class Zoo{
public:
  Zoo();
  virtual ~Zoo();
  virtual void updateAll();
  //And various other functions dealing with animals
private:
  vector<animal*> animals
}

现在假设我想创建一个 bird_zoo，并且我想重用大部分代码用于 Zoo 类和 Animal 类。

所以我做鸟类

class Bird : public Animal{
public:
  Bird();
  virtual ~Bird();
  //all the various functions derived from Animal class
  virtual void fly(); //New function that Animal didn't have
}

class Bird_Zoo : public Zoo{
public:
  Bird_Zoo();
  virtual ~Bird_Zoo();
  //And various other functions dealing with animals, derived from Zoo
  virtual void flyAll(); //New function that Zoo didn't have
private:
  //vector<??????> birds
}

我怎么得到这个Bird_Zoo对付飞鸟的功能有哪些？如果我留在vector<Animal*>来自 Zoo 类，我如何调用 fly() ？我真的必须把它转换到Bird*吗？每次？有没有办法在概念上“重载”vector<Animal*>作为vector<Bird*> ,这样所有旧的 Zoo 功能仍然可以正常工作？

谢谢。

Answer 1

另一种可能性是使用模板。

class Zoo {
  // ...
  virtual void updateAll() = 0;
};

template <typename T,
          typename = typename enable_if<is_base_of<Animal, T>::value>::type>
class ZooWithAVector : public AbstractZoo {
public:
  virtual void updateAll() { /* ... */ }
  // Various functions dealing with T-animals
private:
  vector<T*> animals;
};

typedef ZooWithAVector<Animal> TypicalZoo;

class BirdZoo : public ZooWithAVector<Bird> {
  virtual void flyAll() { /* work with the vector<Bird> */ }
};