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如何使C中的入侵树类使用泛型?

intrusive-containers data-structures c#

Andrew Russell · 技术社区 · 15 年前

在C我有一个 侵入的 树结构如下:

public abstract class Node
{
    Container parent;
    Node nextNode;
    Node previousNode;

    public abstract class Container : Node
    {
        Node firstChild;
        Node lastChild;
    }
}

可以添加到树中的各种对象继承自 Node 或 Container 取决于他们是否可以生孩子。

通过制作 集装箱 一个内部类,它意味着它可以访问 结点 用于管理容器的子级列表。

这一切都很好。但现在我希望它是通用的,这样我可以在维护类型安全的同时重用它——基本上将所有树功能移动到节点上方的通用类,以及节点和容器之间的其他类。下面是我要做的事情的大致设计:

public abstract class GenericNode<Node, Container>
    where Node : GenericNode<Node, Container>
    where Container : GenericNode<Node, Container>.GenericContainer
{
    Container parent;
    Node nextNode;
    Node previousNode;

    public abstract class GenericContainer : Node
    {
        Node firstChild;
        Node lastChild;
    }
}

当然,这不起作用,因为你不能 GenericContainer 继承自 结点 编译错误 CS0689 )即使我放弃了内部类需求(比如 internal 只是在我自己的库中小心一点)我仍然无法找出一个设计不会遇到同样的问题(和错误)。

(我不认为我必须这样做,但我只是想说清楚: 我不想“修复”编译错误 我也不想寻找一个简单的树实现。这是一个容器设计问题。)

所以现在我有点头疼。有人对如何设计这个东西有更好的想法吗?

编辑:一定要看看 this answer 这是设计的另一个障碍,它试图使用扩展方法来避免将类“注入”到继承层次结构中的问题(但不幸的是不能完全工作)。

6 回复 | 直到 15 年前

Leon van der Walt 15 年前

{
    MyNode n = new MyNode();
    var c = new MyNode.MyContainer();
    c.AddChild(n);

    MySubNode s = new MySubNode();
    c.AddChild(s);

    OtherNode o = new OtherNode();
    o.AddChild(o);

    //compiler doesn't allow this, as you'd expect:
    //c.AddChild(o);
}        

public interface IContainer<TContainerType, TNodeType>
    where TNodeType : GenericNode<TContainerType, TNodeType>
    where TContainerType : TNodeType, IContainer<TContainerType, TNodeType>
{
}

public static class ContainerExtensions
{
    public static void AddChild<TContainerType, TNodeType>(this IContainer<TContainerType, TNodeType> self, TNodeType node)
        where TNodeType : GenericNode<TContainerType, TNodeType>
        where TContainerType : TNodeType, IContainer<TContainerType, TNodeType>
    {
        GenericNode<TContainerType, TNodeType>.AddChild(self as TContainerType, node);
    }
}

public class GenericNode<TContainerType, TNodeType>
    where TNodeType : GenericNode<TContainerType, TNodeType>
    where TContainerType : GenericNode<TContainerType, TNodeType>
{
    TContainerType parent;
    TNodeType nextNode;
    TNodeType previousNode;

    // Only used by Container
    TNodeType firstChild;
    TNodeType secondChild;

    internal static void AddChild(TContainerType container, TNodeType node)
    {
        container.firstChild = node;
        node.parent = container;
    }
}

public class MyNode : GenericNode<MyContainer, MyNode>
{        
}

public class MyContainer : MyNode, IContainer<MyContainer, MyNode>
{
}

public class MySubNode : MyNode
{
}

public class OtherNode : GenericNode<OtherNode, OtherNode>, IContainer<OtherNode, OtherNode>
{
}

Sunny 15 年前

public class Tree<T> : ITree<T> where T : INode{
    public T RootNode { get; private set; }
    public Tree(T rootNode){
        RootNode = rootNode;
    }
}

public interface ITree<T> where T : INode{
    T RootNode { get; }
}

public interface INode{
    INode Parent { get; }
    List<INode> Children { get; }
}

internal class Node : INode{
    public INode Parent { get; private set; }
    public List<INode> Children { get; private set; }
    public Node( INode parent, List<INode> children = new List<INode>()){
        Parent = parent;
        Children = children;
    }
}

Lunivore 15 年前

public abstract class GenericNode<Node, Container>
    where Node : GenericNode<Node, Container>
    where Container : GenericNode<Node, Container>.GenericContainer<Node>
{
    Container parent;
    Node nextNode;
    Node previousNode;

    public abstract class GenericContainer<Branch> where Branch: GenericNode<Node, Container> 
    {
        private Leaf firstChild;
        private Leaf secondChild;
    }
}

Branch Node GenericNode

Dan Bryant 15 年前

public interface ITagged<T>
{
    T Tag { get; set; }
}

public sealed class Tree<T>
{
    //All Tree operations are performed here (add nodes, remove nodes, possibly move nodes, etc.)
    //Nodes are only exposed as 'ITagged<T>', such as:
    public ITagged<T> Root { get; private set; }

    public IEnumerable<ITagged<T>> GetChildren(ITagged<T> item)
    {
        //Cast to Container and enumerate...
    }

    //Several other tree operations...

    private class Node : ITagged<T>
    {
        Container parent;
        Node nextNode;
        Node previousNode;

        public T Tag { get; set; }
    }

    private class Container : Node
    {
        Node firstChild;
        Node lastChild;
    }
}

Andrew Russell 15 年前

public abstract class GenericNode<Node, Container>
    where Node : GenericNode<Node, Container>
    where Container : Node
{
    Container parent;
    Node nextNode;
    Node previousNode;

    // Only used by Container
    Node firstChild;
    Node secondChild;

    public static class ContainerHelpers
    {
        public static void AddChild(Container c, Node n)
        {
            c.firstChild = n; // not a real implementation ;)
            n.parent = c;
        }
    }
}

// EDIT: This does not work correctly! (see example below)
public static class GenericNodeExtensionMethods
{
    public static void AddChild<Node, Container>(this Container c, Node n)
        where Node : GenericNode<Node, Container>
        where Container : Node
    {
        GenericNode<Node, Container>.ContainerHelpers.AddChild(c, n);
    }
}

//
// Example Usage
//

public class MyNode : GenericNode<MyNode, MyContainer>
{
}

public class MyContainer : MyNode
{
}

public class MySubNode : MyNode
{
}

public class OtherNode : GenericNode<OtherNode, OtherNode>
{
}


class Program
{
    static void Main(string[] args)
    {
        MyNode n = new MyNode();
        MyContainer c = new MyContainer();
        c.AddChild(n);

        MySubNode s = new MySubNode();
        //
        // This does not work because it tries to fill the generic in the
        // extension method with <MySubNode, MyContainer>, which does not
        // fulfil the constraint "where Container : Node".
        //
        //c.AddChild(s);

        OtherNode o = new OtherNode();
        o.AddChild(o);
    }
}

Claus Jørgensen 15 年前

public abstract class GenericNode<TNode, TContainer>
    where TNode : GenericNode<TNode, TContainer>
    where TContainer : GenericNode<TNode, TContainer>.GenericContainer
{
    public TContainer Parent { get; set; }
    public TNode Next { get; set; }
    public TNode Previous { get; set; }

    public abstract class GenericContainer : GenericNode<TNode, TContainer>
    {
        public TNode FirstChild { get; set; }
        public TNode LastChild { get; set; }
    }
}