Question

我有以下几类:

template <typename T>
class Fixed2DContainer {

    T* ptr;

public:
    const int total_cols;
    const int total_rows;

    Fixed2DContainer(int cols, int rows);
    T& operator()(int col_n, int row_n);
    ~Fixed2DContainer();

private : //disallow copy
    Fixed2DContainer& operator=(const Fixed2DContainer&);
    Fixed2DContainer operator()(const Fixed2DContainer&);
};

Now I d like to specialize this template for some class so that the only change is that I can have an another constructor. Basically I want to be able to do:

Fixed2DContainer<Image>("filename.jpg");

is there an elegant way to do this? I am fairly new to template so i have no idea of the difficulty

Answer 1

我在先前评论中所说的话的快速例子......

template <typename T>
class Fixed2DContainerBase {

  T* ptr;

public:
  const int total_cols;
  const int total_rows;

  Fixed2DContainerBase(int cols, int rows);
  T& operator()(int col_n, int row_n);
  ~Fixed2DContainerBase();

private : //disallow copy
  Fixed2DContainerBase& operator=(const Fixed2DContainerBase&);
  Fixed2DContainerBase(const Fixed2DContainerBase&);
};

// primary template
template <typename T>
class Fixed2DContainer : public Fixed2DContainerBase<T> {

  Fixed2DContainer(int cols, int rows);
  ~Fixed2DContainer();
};

// explicit specialization
template <>
class Fixed2DContainer<Image> : public Fixed2DContainerBase<Image> {

  Fixed2DContainer(int cols, int rows);
  Fixed2DContainer(const std::string&);
  ~Fixed2DContainer();
};

N.B. 由于基类是不可计量的,因此衍生的班级也将如此。如果所有清理工作都能由主线主人进行,则可能没有必要在衍生课程中确定一位主子。

Answer 2

如果您的编辑支持的话,C++11有主导建筑设计器<>m>,在你希望做以下工作时,会得到很多帮助:

template <typename T> class Base {}; // has all the implementation template <typename T> class Template { using Base::Base; //Template() = delete; // You might need this if you don t want // the default constructor }; template <> class Template<int> { using Base::Base; Template( std::string const & x ) {} //Template() = delete; // You might need this if you don t want // the default constructor };

Answer 3

我有同样的问题。不幸的是,每个建筑商都必须在通用模板中存在。你们可以避免有人在经营时使用错误的构造;

template <typename T>
class Fixed2DContainer {

    // omitted

    Fixed2DContainer(string fileName)
    {
        // Do not allow construction of Fixed2DContainer with
        // string argument in general case
        ASSERT(false);
        // or
        throw new ExceptionType("Not implemented");
    }

    // omitted
};

template<>
class Fixed2DContainer<Image> {

    // omitted

    Fixed2DContainer(string fileName)
    {
        // Actual construction code
    }

    // omitted
};

优先选择阿瑟,因为你的法典将打破主张,而例外情形中,它会中断捕获量,使其稍微难以减少。

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