如何创建模板类对象的数组？ [英] How to create an array of templated class objects?

问题描述

我没有做任何的C ++编程相当长的一段时间，我决定，我会更动它在我的业余时间一点点，所以我决定给我写一个小数据库程序只是为了好玩，我有麻烦创建模板类对象的数组。

I haven't done any C++ programming for quite some time and I decided that I would mess around with it a little bit in my spare time so I decided to write me a little database program just for fun and I'm having trouble with creating an array of templated class objects.

我已经是这样的类，我想用它来重新present一个字段​​在数据库中记录。

What I have is this class which I want to use to represent a field in a database record.

template <class T, int fieldTypeId>
class Field
{
private:
    T field;
    int field_type;
public:
    // ...
};

和我想使用这个类的数组使用此类重新present记录在数据库中。

And I want to use an array of that class to represent a record in a database using this class.

class Database_Record
{
private:
    int id;
    Field record[];
public:
    Database_Record(int);
    Database_Record(int, Field[]);
   ~Database_Record();
};

在哪里我被困在位于 Database_Record 类阵列的创建，因为这是模板类对象，每个元素可能是一个不同类型的数组我不知道我需要怎样声明，因为该数组。就是我试图做甚至有可能还是我将它的错误的方式？任何帮助将大大AP preciated。

Where I'm stuck at is the creation of the array in the Database_Record class since that is an array of templated class objects with each element possibly being of a different type and I'm not sure how I need declare the array because of that. Is what I'm trying to do even possible or am I going about it the wrong way? Any help would be greatly appreciated.

推荐答案

字段＆LT; T1＆GT; 和字段＆LT; T2＆GT; 是两个完全不同的类型。要在矢量对待他们，你需要generialize然后某处。你可以写 AbstractField 和

Field<T1> and Field<T2> are two completely different types. To treat them in a vector you need to generialize then somewhere. You may write AbstractField and

struct AbstractField{
  virtual ~AbstractField() = 0;
};

template<class T,int fieldTypeId>
class Field: public AbstractField{
  private:
    T field;
  public:
    const static int field_type;
  public:
    virtual ~Field(){}
};

class Database_Record{
  std::vector<AbstractField*> record; 
  public:
    ~Database_Record(){
      //delete all AbstractFields in vector
    }
};

然后保持 AbstractField 的矢量。还可以使用矢量而不是 [] 。使用 AbstractField * 而不是 AbstractField 和写入至少一个纯虚在 AbstractField 。

and then keep a vector of AbstractField. also use vector instead of []. Use AbstractField* instead of AbstractField and write at least one pure virtual in AbstractField.

您可能会使 AbstractField 纯虚的析构函数。不要忘记删除所有 AbstractField 秒。在〜Database_Record（）

you may make the destructor of AbstractField pure virtual. and don't forget to delete all AbstractFields. in ~Database_Record()

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