应该删除工厂方法创建的对象在哪里？

Question

创建对象的方式和位置应该returnShapeType删除？
这是一个工厂方法演示程序.

请出示代码.

class Shape
{
public:
    Shape() {}
    virtual void print() {std::cout << "\nFrom shape print";}
};

class Triangle: public Shape
{
public:
    Triangle(){}
    virtual void print() {std::cout << "\nFrom triangle print";}
};

class Rectangle: public Shape
{
public:
    Rectangle(){}
    virtual void print() {std::cout << "\nFrom rect print";}
};

class CreateShapeObject
{
public:
    CreateShapeObject() {}

    Shape *returnShapeType( std::string arg )
    {
        if (arg == "Triangle")
            return new Triangle;
        else if (arg == "Rectangle")
            return new Rectangle;
    }
};

////////////

class EndDeveloper
{
public:
    CreateShapeObject obj;

    EndDeveloper()
    {
        Shape *p = obj.returnShapeType("Triangle");
        p->print();

        Shape *q = obj.returnShapeType("Rectangle");
        q->print();


    }
};

Answer 1

使用原始指针很容易出错.使用unique_ptr:

std::unique_ptr<Shape> returnShapeType(const std::string& arg)
{
    if (arg == "Triangle")
        return std::make_unique<Triangle>();
    else if (arg == "Rectangle")
        return std::make_unique<Rectangle>();
    throw std::invalid_argument("Invalid shape");
}

您可以方便地使用它auto:

auto shape = obj.returnShapeType("Triangle");

unique_ptr也可以隐式转换为shared_ptr:

std::shared_ptr<Shape> shape = obj.returnShapeType("Triangle");