具有公共抽象基类的对象集合 [英] Collection of objects with common Abstract base class

问题描述

我有一个叫做泛型的抽象类，实现如下:

I have an abstract class called generic, implemented as follows:

public abstract class generic
{
    public string creatorID { get; set; }
    public string itemID { get; set; }
    public string name { get; set; }
    public DateTime creationDate { get; set; }
    public string pageName { get; set; }
    ...
}

这是通过几个类来实现的，比如:

This is implemented through several classes, such as:

public class file : generic
{
    public file(string _itemID, string host, string languageReferenceID)
    {
        DataTable dt = GetRecordsFromDatabase(string _itemID, string host, string languageReferenceID);
        if (dt.Rows.Count > 0)
            setParameters(dt.Rows[0]);
        ...
    }

    private void setParameters(DataRow dr)
    {
        creatorID = dr["f_MemberID"].ToString();
        itemID = dr["f_ID"].ToString();
        name = dr["f_Name"].ToString();
        creationDate = DateTime.Parse(dr["f_DateCreated"].ToString());
        pageName = "files";
        ...
    }
}

我想要做的是创建一个该抽象泛型类的不同实例化的对象列表.这是我正在尝试做的:

What I'm trying to do is create a List of objects of different instantiations of that abstract generic class. Here's what I'm attempting to do:

    public List<generic> getAlerts(string host, string languageReferenceID)
    {            
        DataTable dt = GetAlertsFromDatabase(host, languageReferenceID);

        List<generic> alertList = new List<generic>();

        foreach (DataRow dr in dt.Rows)
        {
            generic g = new generic();

            g.itemID = dr["itemID"];
            g.description = dr["description"];
            g.pageName = dr["pageName"];

            g.Add(m);
        }

        return alertList;
    }

现在，当然，这是抛出一个错误:

Now, of course, this is throwing an error on the line with:

generic g = new generic();

由于泛型是抽象类，所以不能实例化为对象.

Since generic is an abstract class, it can't be instantiated as an object.

我的问题是 - 考虑到我列出的要求，我该如何实现我的目标?我是否应该创建一个实现抽象类泛型的新类，其唯一目的是实例化泛型类型的列表?这对我来说似乎是一个奇怪的解决方案，但这是我现在唯一能想到的.

My question is - how do I accomplish my objective, given the requirements I've listed? Should I create a new class implementing the abstract class generic, for the sole purpose of instantiating lists of type generic? That seems like an odd solution to me, but it's the only thing I can think of right now.

推荐答案

对我来说，这看起来像 a类工厂.

To me, this looks like a class factory.

您需要一个方法，它接受一个 DataRow，查看它的字段，并决定应该为该行创建 generic 的哪个子类.然后它创建适当的对象newObj，调用newObj.setParameters(dr)，并返回newObj.

You need a method that takes a DataRow, looks at its fields, and decides which subclass of generic should be created for that row. Then it creates the appropriate object newObj, calls newObj.setParameters(dr), and returns newObj.

最好是，实际的工厂方法不采用 DataRow，而是采用一个标量值(int、string 等)来指示要创建的类型.

Preferably, the actual factory method doesn't take a DataRow, but rather just the one scalar value (int, string, whatever) that indicates the type to be created.

也许类工厂是通过依赖注入传入的；您可以对此进行简单或详细说明.

Perhaps the class factory is passed in by dependency injection; you could go simple or elaborate on this.

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