c++ - 抽象类 c++(错误 LNK 2001 : unresolved external symbol)

Question

当我创建一个实现基类虚函数的子类的对象时出现此错误。

error LNK2001: unresolved external symbol "public: virtual void __thiscall CateringOrder::[Order]::calcTotals(void)" (?calcTotals@?QOrder@@CateringOrder@@UAEXXZ)

而我的代码是

class Order
{
private:
    float SANDWICH_PRICE;
    float TOCOS_PRICE;

public:
    string customerType;
    int NumberOfSandwiches;
    int NumberOfTacos;
    float SandwichSubtotal;
    float Subtotal;
    float TacosSubtotal;
    float Total;
    int TotalItems;

    virtual void calcTotals()=0;

    virtual ~Order(){};



};

//子类1

class ConsumerOrder:public Order{
private:
    float SALES_TAX_RATE;
public:
    string CustomerName;
    float SalesTax;
    void calcTotals() override;
    string ToString();

};

//子类 2

class CateringOrder: public Order
{

public:
    string CustomerCode;
    float DeliveryFee;
    bool PreferredCustomer;
    void Order::calcTotals(void) override;
    string ToString();

};

//其他类

static class Validation
{
public:
    bool CheckCustomerCode();
    bool CheckCustomerType();
    float CheckDeliveryFee();
    int CheckItem();

};

现在，当我创建基类的对象时，编译后显示错误。

bool Validation::CheckCustomerCode()
{
CateringOrder obj;

string tempCode = obj.CustomerCode;

return true;
}

Answer 1

好吧，您得到的链接器错误表明您从未为

提供定义

void CateringOrder::calcTotals(void) {…}

除此之外，写这样的东西:

void Order::calcTotals(void) override;

在类定义中是不合法的 C++。虽然这种非标准语法适用于 Visual C++ 编译器，但仅出于兼容性原因保留它。正确的版本是简单地写

void calcTotals(void) override;