在编程过程中，我收到一条我无法解决的错误消息。请帮忙！ 关于第23行（声明了MAA类的地方）的错误消息：“未定义对'vtable for MAA的引用'”
class MAA : public IAA {
friend class Builder;
public:
void executar() override;
private:
void autenticar() override;
};
class IAA {
friend class Builder;
public:
virtual void executar() = 0;
virtual ~IAA() {}
private:
virtual void autenticar() = 0;
protected:
Controller* controller = nullptr;
ISA* servico = nullptr;
};