使用工厂方法时的编译器错误：无法转换 'const std::pair<char* const

Question

我正在尝试为一个软件编写代码，该软件会为模拟生成不同类型的 "Cars"。我想让用户能够选择对象的数量 "cars" 进行模拟，我认为工厂方法将是最好的方法。

这是我遇到问题的代码部分：

typedef map<char *,Factory *> CarFactories;
CarFactories carFactories;
carFactories["Private"]   = new privateFactory();
carFactories["Police"]    = new policeFactory();
carFactories["Ambulance"] = new ambulanceFactory();

cout << "Self-Driving Cars Simulatator V1.0" << endl;
cout << "Enter number of vehicles in the simulation > " <<endl;
cin >> numCars;
    for(int i = 0; i <= numCars; i++){

        int numType;
        char vehicleType;
        //char *ptrVT;

        cout << "enter the number vehicle type to add > " << endl;
        cout << "   1- Private Vehicle." << endl;
        cout << "   2- Police Car."      << endl;
        cout << "   3- Ambulance."       << endl;
        cin >> numType;

        if (numType == 1)
            vehicleType = 'Private';
        else if (numType == 2)
            vehicleType = 'Police';
        else if (numType == 3)
            vehicleType = 'Ambulance';
        else
            cout << "Invalid entry.";

        //ptrVT = &vehicleType;


      CarFactories::const_iterator it=carFactories.find("Police");
        if (it!=carFactories.end())
        Factory *factory = *it; //error 1
        Private *priv  = factory->create(); //error 2
        Police  *pol   = factory->create(); //error 3
        Ambulance *amb = factory->create(); //error 4
        }

at //error 1 我得到：错误：无法在初始化中将‘const std::pair’转换为‘Factory*’|

at //error 2,3, & 4 我得到：错误：从“Car*”到“Private/Police/Ambulance*”的无效转换 [-fpermissive]

这是我的工厂：

class Factory
{
        public:
        virtual Car *create() = 0;
};




    class privateFactory : public Factory {

        public:
            Private *create() { return new Private();}

    };



    class policeFactory : public privateFactory {

        public:
            Police *create() { return new Police();}
    };



    class ambulanceFactory : public Factory {

        public:
            Ambulance *create() { return new Ambulance();}
    };

工厂没有错误。

Ambulance 和 Private 派生自 Car。 police来源于private.

任何帮助将不胜感激。

汽车，私人，警察类：

class Car
{
    public:
        Car();
                ..setters and getters.

        ~Car();

    protected:
        ...double, int, chat variables...


};


class Police : public Private
{
    public:
        Police();
        ..setters and getters.
        ~Police();

    protected:
      ...  int variables...;
};

等等。

Answer 1

对于第一个错误，*它将 return 迭代器中正确位置的对。所以你得到的是你应该做的对 (*it).second.
对于所有其他错误，汽车、救护车和警察应该从汽车上驾驶，它不必直接，例如，如果私人从汽车上驾驶，而不是警察从汽车上驾驶，那还好（你做得很好），但你的问题是你在不使用 static_cast 或 c cast 的情况下进行向下转换。

Police* police = static_cast<Police*>(factory->create())

并且您的代码不适用于其他类型，您需要像对待警察一样获取每种类型。

正如 thia post 中所述：Can't downcast because class is not polymorphic?.

使用工厂方法时的编译器错误：无法转换 'const std::pair<char* const

Compiler Error When Using Factory Method: cannot convert 'const std::pair<char* const

c++

simulation

containers

factory

stl