C ++抽象类没有纯虚函数？ [英] C++ abstract class without pure virtual functions?

问题描述

我有一个基类

  class ShapeF 
 {
 public：
 ShapeF （）; 
 virtual〜ShapeF（）; 
 
 inline void SetPosition（const Vector2& inPosition）{mPosition.Set（inPosition）; } 
 
 protected：
 Vector2 mPosition; 
} 
  

显然有一些ommitied代码，但你得到的点。
我使用它作为一个模板，并使用一些有趣的（枚举）枚举，一种确定我使用什么样的形状的方法

  class RotatedRectangleF：public ShapeF 
 {
 public：
 RotatedRectangleF（）; 
 virtual〜RotatedRectangleF（）; 
 protected：
 float mWidth; 
 float mHeight; 
 float mRotation; 
} 
  

ShapeF通过定位来完成它的工作，是。
它有访问器和变异符，但没有方法。

我可以让ShapeF一个抽象类，以确保没有人尝试和实例化一个ShapeF类型的对象？ / p>

通常情况下，这可以通过在ShapeF中拥有一个纯虚函数来实现。

  // ShapeF.h 
 virtual void Collides（const ShapeF& inShape）= 0; 
  

但是，我目前正在处理一个单独的类中的碰撞。
我可以移动一切，但我想知道是否有一个方法来创建一个类抽象..没有纯虚函数。

解决方案

您可以声明，并实现一个纯虚拟析构函数：

  class ShapeF 
 {
 public：
 virtual〜ShapeF（）= 0; 
 ... 
}; 
 
 ShapeF ::〜ShapeF（）{} 
  

从你已经有，并将阻止 ShapeF 直接实例化。派生类不需要更改。

I have a base class

class ShapeF
{
public:
    ShapeF();
    virtual ~ShapeF();

    inline void SetPosition(const Vector2& inPosition) { mPosition.Set(inPosition); }

protected:
    Vector2 mPosition;
}

Obviously with some ommitied code, but you get the point. I use this as a template, and with some fun (ommited) enums, a way to determine what kind of shape i'm using

class RotatedRectangleF : public ShapeF
{
public:
    RotatedRectangleF();
    virtual ~RotatedRectangleF();
protected:
    float mWidth;
    float mHeight;
    float mRotation;
}

ShapeF does its job with the positioning, and an enum that defines what the type is. It has accessors and mutators, but no methods.

Can I make ShapeF an abstract class, to ensure nobody tries and instantiate an object of type ShapeF?

Normally, this is doable by having a pure virtual function within ShapeF

//ShapeF.h
virtual void Collides(const ShapeF& inShape) = 0;

However, I am currently dealing with collisions in a seperate class. I can move everything over, but i'm wondering if there is a way to make a class abstract.. without the pure virtual functions.

解决方案

You could declare, and implement, a pure virtual destructor:

class ShapeF
{
public:
    virtual ~ShapeF() = 0;
    ...
};

ShapeF::~ShapeF() {}

It's a tiny step from what you already have, and will prevent ShapeF from being instantiated directly. The derived classes won't need to change.

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