从向量（c ++）中调用派生类函数 [英] Calling derived class functions from within a vector (c++)

问题描述

我有两个类：

class Object {
public:
  Object();
  virtual void update();
  virtual void draw();

private:

protected:
  int x, y, tick;

}

和

class Unit : public Object {
public:
  Unit();
  void update();

private:

protected:

}

然后在sepparate .cpp文件中定义构造函数和函数。

I then define the constructors and functions in sepparate .cpp files.

下面是对象的定义：

Object::Object() {
  x = y = 0;
};

Object::update() {
  tick ++;
};

Object::draw() {
  // All my draw code is in here.
};

并且单位：

Unit::Unit() : Object() {

};

Unit::update() {
  Object::update();
  // Then there's a bunch of movement related code here.
};

一切正常，但我遇到一个问题，当尝试从向量内调用函数。

Everything works fine individually, but I run into a problem when trying to call functions from within a vector.

vector<Object> objects;

然后在我的void main（）中执行：

I then do this in my void main():

for (int i = 0; i < objects.size(); i ++) {
  objects[i].update();
  objects[i].draw();
};

这样绘制一切正常，但它只调用update（）的对象版本而不是定义的版本由派生类。我必须为我从派生的Object类派生的每个类型为它工作，或者有另一种方法来调用派生的函数？

This draws everything fine, but it only calls the Object verson of update() not the version as defined by the derived class. Do I have to make a vector for each type that I derive from the Object class for it to work, or is there another way to call the derived functions?

感谢提前 - Seymore

Thanks in advance - Seymore

推荐答案

是的，它调用 class Object 因为你有一个 class Object 对象的向量：

Yes, it calls methods of class Object, because you have a vector of class Object objects:

vector<Object> objects; // stores instances of class Object

可能的解决方案是使用指针向量：

The possible solution is to use a vector of pointers:

vector<Object*> objects;
objects.push_back( new Unit() );

然后通过指针调用：

for (int i = 0; i < objects.size(); i ++) {
    objects[i]->update();
    objects[i]->draw();
}

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