Question

我有两个接口，一个包含另一个接口的列表，我希望有一个实现第一个接口的类，但是有一个实现第二个接口而不仅仅是接口列表的另一个类的列表。例如：

namespace TestInheritance
{
    public interface IBookShelf
    {
        long Stuff { get; set; }
        List<IBook> Books { get; set; }
    }
    public interface IBook
    {
        string Name { get; set; }
    }
    public class BookShelf : IBookShelf
    {
        public long Stuff { get; set; }
        public List<Book> Books { get; set; }
    }
    public class Book : IBook
    {
        public string Name { get; set; }
    }
}

显然它不喜欢这个。是否有正确的方法来做我想做的事情，或者我只需要让BookShelf拥有List<IBook>并将每个IBook投放到Book时我想用它吗？寻找可以帮助我在这里的模式。感谢。

Answer 1

在将通用参数约束为IBookShelf

的情况下，可以使IBook通用

然后你可以：

public interface IBookShelf<T> where T : IBook
{
    long Stuff { get; set; }
    List<T> Books { get; set; }
}

public class BookShelf : IBookShelf<Book>
{
    public long Stuff { get; set; }
    public List<Book> Books { get; set; }
}

Answer 2

目前尚不清楚正在尝试做什么 - 而且怀疑它甚至不清楚。为什么您特别希望BookShelf.Books成为List<Book>？为什么限制本身仅包含Book值而不是IBook值？我建议你考虑在这种情况下你想要发生什么：

public class EvilBook : IBook
{
    public string Name { get; set; }
}

IBookShelf bookShelf = new BookShelf() { Books = new List<Book>() };
bookShelf.Books.Add(new EvilBook());

该代码中没有任何内容可疑¹，包含您提供的接口 - 但最终会在EvilBook中添加List<Book>，这肯定不是对。我经常发现，如果编译器阻止我做某事，那么考虑一下我可能遇到的问题是有用的，如果它让我继续我的坏主意。

您可能希望考虑制作IBookShelf通用：

public interface IBookShelf<T> where T : IBook
{
    long Stuff { get; set; }
    List<T> Books { get; set; }
}

然后：

public class BookShelf : IBookShelf<Book>

......但这实际上取决于你想要达到的目标。

您可能还想问自己，您是否真的首先需要IBook界面...以及您是否真的需要{{1}的公共可写属性}。

¹无论如何，编译器会认识到：）

Answer 3

这样的事情怎么样：

namespace TestInheritance
{
    public interface IBookShelf <TBook> where TBook : IBook
    {
        long Stuff { get; set; }
        List<TBook> Books { get; set; }
    }
    public interface IBook
    {
        string Name { get; set; }
    }
    public class BookShelf : IBookShelf<Book>
    {
        public long Stuff { get; set; }
        public List<Book> Books { get; set; }
    }
    public class Book : IBook
    {
        public string Name { get; set; }
    }
}

Answer 4

一般来说，施法是可疑的，最好避免。这是一个很好的信号，表明某些事情是不对的。

修复需要更改的代码

public List<Book> Books { get; set; }

到

public List<IBook> Books { get; set; }

你可以而且应该更多地概括一些事情。什么样的书架不允许其他物品？我还没看到一个。考虑一下：



using System;
using System.Collections.Generic;
using System.Linq;

public class Program
{
public interface IShelf
{
    long Stuff { get; }
    List<IShelfItem> Items { get; }
}
public interface IShelfItem
{
    string Name { get; }
    string Thought {get; set;}//What do I think about it?
}
public class Shelf : IShelf
{
    public Shelf(long stuff, string color) 
    {
        Stuff = stuff;
        Items = new List<IShelfItem>();
        Color = color;
    }

    public long Stuff { get; private set; }
    public List<IShelfItem> Items { get; private set; }//Note, you can still add to the list.
    public string Color { get; set; }

}
public class Book : IShelfItem
{
    public Book( string name, string thought ) {
        Name = name;
        Thought = thought;
    }
    public string Name { get; private set; }//Books that are on shelves don't really change their name;
    public string Thought { get; set; }

    public string BookSpecificProperty { get; set; }
}


public static void Main()
{
    Shelf myShelf = new Shelf(42, "Dull boring grey");

    myShelf.Color = "Red";


    IShelf myIShelf = myShelf;
    //myIShelf.Color = "Red"; - 'IShelf' does not contain a definition for 'Color'

    myShelf.Items.Add( new Book("Title 1", "Such a great book" ) );

    //Eos pass

    var book = myShelf.Items.SingleOrDefault( i => i.Name == "Title 1" );
    if( book != null ) {
        book.Thought = "I used to think it was such a great book. It's just OK";
        //book.BookSpecificProperty = "X"; - 'IShelfItem' does not contain a definition for 'BookSpecificProperty'
    }
}

using System; using System.Collections.Generic; using System.Linq; public class Program { public interface IShelf { long Stuff { get; } List<IShelfItem> Items { get; } } public interface IShelfItem { string Name { get; } string Thought {get; set;}//What do I think about it? } public class Shelf : IShelf { public Shelf(long stuff, string color) { Stuff = stuff; Items = new List<IShelfItem>(); Color = color; } public long Stuff { get; private set; } public List<IShelfItem> Items { get; private set; }//Note, you can still add to the list. public string Color { get; set; } } public class Book : IShelfItem { public Book( string name, string thought ) { Name = name; Thought = thought; } public string Name { get; private set; }//Books that are on shelves don't really change their name; public string Thought { get; set; } public string BookSpecificProperty { get; set; } } public static void Main() { Shelf myShelf = new Shelf(42, "Dull boring grey"); myShelf.Color = "Red"; IShelf myIShelf = myShelf; //myIShelf.Color = "Red"; - 'IShelf' does not contain a definition for 'Color' myShelf.Items.Add( new Book("Title 1", "Such a great book" ) ); //Eos pass var book = myShelf.Items.SingleOrDefault( i => i.Name == "Title 1" ); if( book != null ) { book.Thought = "I used to think it was such a great book. It's just OK"; //book.BookSpecificProperty = "X"; - 'IShelfItem' does not contain a definition for 'BookSpecificProperty' } }

继承具有List <interface>的接口作为属性问题</interface>

4 个答案: