將unique_ptr傳遞給對象會引發錯誤

Question

我正在學習構建器設計模式和智能指針。
因此，我嘗試在代碼中完全使用smart_ptr。 但是，當我使用unique_ptr在main中創建實例並將其傳遞給Contractor對象時，它將引發錯誤。

如果我在承包商類和main類中用shared_ptr替換unqiue_ptr。 該編運行正常，但未調用任何析構函數。

以下是我使用unique_ptr時遇到的錯誤。

 error: call to implicitly-deleted copy constructor of 'std::unique_ptr<HouseBuilder>'
 Contractor *ctr1 = new Contractor(lavishHouseBldr);

/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/memory:2621: copy constructor is implicitly deleted because 'unique_ptr<HouseBuilder, std::__1::default_delete<HouseBuilder> >' has a user-declared move constructor
_LIBCPP_INLINE_VISIBILITY unique_ptr(unique_ptr&& __u) _NOEXCEPT
                              ^
passing argument to parameter 'houseBuilder' here
 Contractor(std::unique_ptr<HouseBuilder>houseBuilder): houseBuilder(std::move( houseBuilder))

下面是我的代碼。

/* Concrete class for the HousePlan interface */
class House
{
private:
  std::string  window, door, bathroom, floor, kitchen;
public:
  void setWindow( string window)
  {
      this->window = window;
  }
  void setDoor( string door)
  {
      this->door = door;
  }
  ~House()
  {
      cout <<"destructor  House called"<<endl;
  }
};
/* Builder class*/
class HouseBuilder
{
public:
    virtual void buildWindow()   = 0;
    virtual void buildDoor()     = 0;
    virtual House* getHouse()    = 0;
    virtual ~HouseBuilder() = 0;
};
HouseBuilder::~HouseBuilder()
{
    std::cout <<"Destructor for housebuilder called";
}
class LavishHouse:public HouseBuilder
{
public:
  LavishHouse( )
  {
      house.reset(new House());
  }
  ~LavishHouse( )
  {
      cout <<"Lavish House Destructor callled"<<std::endl;
  }
  void buildWindow()
  {
     house->setWindow(" French Windows");
  }

  void buildDoor()
  {
      house->setDoor(" woodenDoor");
  }
  House* getHouse()
  {
      return  house.get();
  }
private:
    std::unique_ptr<House> house;
};
/* The Director. Consturct director*/

class Contractor
{
public:
    Contractor(std::unique_ptr<HouseBuilder>houseBuilder): houseBuilder(std::move( houseBuilder))
    {

    }
   /* Contractor(HouseBuilder*houseBuilder): houseBuilder(houseBuilder)
    {

    }*/
    ~Contractor()
    {
        cout <<"destruct contractor"<<std::endl;
    }

    House *getHouse()
     {
      return houseBuilder->getHouse();
     }

     void buildHouse()
     {
      houseBuilder->buildWindow();
      houseBuilder->buildDoor();
     }
private:
    std::unique_ptr<HouseBuilder> houseBuilder;

};

/* Example on how to use the Builder design pattern */
int main()
{

std::unique_ptr< HouseBuilder> lavishHouseBldr( new LavishHouse() );
 Contractor *ctr1 = new Contractor(lavishHouseBldr); // error!!!!!

 ctr1->buildHouse();
 House *house1 = ctr1->getHouse();
 cout<<"Constructed: "<<house1<< std::endl;
 return 0;
}

Answer 1

lavishHouseBldr是一個左值，不能移動； 您還需要在lavishHouseBldr std::move上應用lavishHouseBldr ，即

Contractor *ctr1 = new Contractor(std::move(lavishHouseBldr));