如何子类化模板化基类？ [英] How to subclass a templated base class?

问题描述

我有以下数据结构：

struct fastEngine { ... }
struct slowEngine { ... }

template<typename T>
class Car {
   T engine;
   vector<T> backupEngines;

   virtual void drive() = 0;
}

class FastCar : public Car<fastEngine> {
   virtual void drive() {
      // use the values of "engine" in some way
   }
}

class SlowCar : public Car<slowEngine> {
   virtual void drive() {
      // use the values of "engine" in some way
   }
}

Car* getCarFromCarFactory() {  // 1
   if (randomNumber == 0)
      return new FastCar();
   else
      return new SlowCar();
}

void main() {
   Car* myCar = getCarFromCarFactory(); // 2
   myCar->drive();
}

编译器在位置1和2处抱怨，因为它要求我定义 Car * ，带有模板参数。我不在乎我正在使用的 Car 的模板版本，我只想要一个指向 Car 的指针，我可以开车。 引擎结构必须是结构，因为它们来自现有代码而我无法控制它们。

The compiler complains at locations 1 and 2 because it requires that I define Car* with template parameters. I don't care what templated version of Car I'm using, I just want a pointer to a Car that I can drive. The engine structs must be structs because they are from existing code and I don't have control over them.

推荐答案

你可以创建一个非模板化的基类 Car< T> 继承，例如

You could create a non-templated base class that Car<T> inherits, e.g.

struct ICar {
    virtual void drive() = 0;
};

template <typename T>
class Car : public ICar {
    // ...
}

int main() { // BTW, it's always `int main`, not `void main`
    ICar *myCar = getCarFromCarFactory();
    myCar->drive();
}

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