Question

我正在学习建筑师设计模式和智能指针所以我试图在我的代码中一直使用smart_ptr。但是当我使用unique_ptr在main中创建实例并将其传递给Contractor对象时，它会抛出错误。

如果我在承包商类和main中用shared_ptr替换unqiue_ptr。编程运行良好但没有析构函数被调用。

以下是我使用unique_ptr时遇到的错误。

 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))

以下是我的代码..

/* 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是左值，无法移动;您还需要在std::move上应用lavishHouseBldr，即

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

将unique_ptr传递给对象会引发错误

1 个答案: