您将如何实现 IEnumerator 接口? [英] How would you implement the IEnumerator interface?

问题描述

我有一个将对象映射到对象的类，但与字典不同的是，它以两种方式映射它们.我现在正在尝试实现一个自定义的 IEnumerator 接口来遍历这些值.

I have a class that map objects to objects, but unlike dictionary it maps them both ways. I am now trying to implement a custom IEnumerator interface that iterates through the values.

public class Mapper<K,T> : IEnumerable<T>, IEnumerator<T>

{
    C5.TreeDictionary<K,T> KToTMap = new TreeDictionary<K,T>();
    C5.HashDictionary<T,K> TToKMap = new HashDictionary<T,K>();

    public void Add(K key, T value)
    {
        KToTMap.Add(key, value);
        TToKMap.Add(value, key);

    }

    public int Count
    {
        get { return KToTMap.Count; }
    }
    

    public K this[T obj]
    {
        get
        {
            return TToKMap[obj];
        }
    }

    public T this[K obj]
    {
        get
        {
            return KToTMap[obj];
        }
    }

    public IEnumerator<T> GetEnumerator()
    {
        return KToTMap.Values.GetEnumerator();
    }

    public T Current
    {
        get { throw new NotImplementedException(); }
    }

    public void Dispose()
    {
        throw new NotImplementedException();
    }

    object System.Collections.IEnumerator.Current
    {
        get { throw new NotImplementedException(); }
    }

    public bool MoveNext()
    {
        ;
    }

    public void Reset()
    {
        throw new NotImplementedException();
    }
}

推荐答案

首先，不要让你的集合对象实现 IEnumerator<>.这会导致错误.(考虑两个线程在同一个集合上迭代的情况).

First, don't make your collection object implement IEnumerator<>. This leads to bugs. (Consider the situation where two threads are iterating over the same collection).

事实证明，正确实现枚举器并非易事，因此 C# 2.0 添加了基于yield return"语句的特殊语言支持.

Implementing an enumerator correctly turns out to be non-trivial, so C# 2.0 added special language support for doing it, based on the 'yield return' statement.

Raymond Chen 最近的系列博客文章(C# 中迭代​​器的实现及其后果")是一个了解速度的好地方.

Raymond Chen's recent series of blog posts ("The implementation of iterators in C# and its consequences") is a good place to get up to speed.

• 第 1 部分:https://web.archive.org/web/20081216071723/http://blogs.msdn.com/oldnewthing/archive/2008/08/12/8849519.aspx
• 第 2 部分:https://web.archive.org/web/20080907004812/http://blogs.msdn.com/oldnewthing/archive/2008/08/13/8854601.aspx
• 第 3 部分:https://web.archive.org/web/20080824210655/http://blogs.msdn.com/oldnewthing/archive/2008/08/14/8862242.aspx
• 第 4 部分:https://web.archive.org/web/20090207130506/http://blogs.msdn.com/oldnewthing/archive/2008/08/15/8868267.aspx

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