如何为实现IEnumerable的班级解构者

发布于 2025-01-29 12:05:53 字数 1567 浏览 2 评论 0 原文

我有一个可以实现Ienumerable的课程。它包含一个实现Ienumerator的getEnumerator（）方法和一个私人类。该类的Current（）方法返回一个是KeyValuepair的对象，即（为了清楚地说明某些代码），

internal sealed class BlockSheet : IEnumerable
{
    public IEnumerator GetEnumerator ()
    {
        return new BlockSheetEnumerator (this);
    }

    private class BlockSheetEnumerator : IEnumerator
    {
        public object Current
        {
            get
            {
                KeyValuePair<Point, Actor> pair = (KeyValuePair<Point, Actor>)this.enumerator.Current;
                return pair;
            }
        }
    }
}

如果我按以下方式调用，则可以正常工作，

foreach (KeyValuePair<Point, Actor> unit in blocksheet)

但是如果我尝试使用Intrant KeyValuepair解剖器并写入

foreach ((Point coordinate, Actor actor) in blocksheet)

，则会得到两个错误：我得到两个错误：

错误cs1061：“对象”不包含“解构”的定义，并且可以找到一个可以找到类型'对象'的第一个参数的可访问的扩展方法'解构'（您是否缺少使用指令或汇编引用？）（CS1061）

错误CS8129：对于类型为“对象”，找不到合适的“解构”实例或扩展方法，具有2个OUT参数和一个void返回类型。（CS8129）

（这是与，但我认为这不适用 - 见下文）

我会认为我会免费获得解构者。我尝试在Blocksheet类和BlockSheetEnumerator类中添加一个解构方法，但没有效果（我觉得这是有道理的，因为这两个类都没有被解构）。

我将使用Visual Studio 2019用于Mac版本8.10.22（Build 11）的Visual Studio 2019来定位.NET 5。当然，我已经成功地使用了带有词典的对象的解构器，向我自己证明这与语言/.NET版本无关。

原文

I have a class that implements IEnumerable. It contains a GetEnumerator() method and a private class that implements IEnumerator. The Current() method of that class returns an object that is a KeyValuePair, i.e (some code elided for clarity)

internal sealed class BlockSheet : IEnumerable
{
    public IEnumerator GetEnumerator ()
    {
        return new BlockSheetEnumerator (this);
    }

    private class BlockSheetEnumerator : IEnumerator
    {
        public object Current
        {
            get
            {
                KeyValuePair<Point, Actor> pair = (KeyValuePair<Point, Actor>)this.enumerator.Current;
                return pair;
            }
        }
    }
}

This works fine if I call as follows

foreach (KeyValuePair<Point, Actor> unit in blocksheet)

but if I try to use the implicit KeyValuePair deconstructor and write

foreach ((Point coordinate, Actor actor) in blocksheet)

then I get two errors:

Error CS1061: 'object' does not contain a definition for 'Deconstruct' and no accessible extension method 'Deconstruct' accepting a first argument of type 'object' could be found (are you missing a using directive or an assembly reference?) (CS1061)

Error CS8129: No suitable 'Deconstruct' instance or extension method was found for type 'object', with 2 out parameters and a void return type. (CS8129)

(This is the same error as, for example, Where's Deconstruct method of KeyValuePair<> struct? but I don't think that applies - see below)

I would have thought that I would get the deconstructor 'for free'. I've tried adding a Deconstruct method to both the BlockSheet class and to the BlockSheetEnumerator class, to no effect (and I don't feel like that makes sense, because neither class is being deconstructed).

I'm targeting .NET 5 with C# 9, using Visual Studio 2019 for Mac version 8.10.22 (build 11). I have, of course, successfully used a deconstructor with an object that is a Dictionary, to prove to myself that it's nothing to do with the language/.NET version.

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人心善变 2025-02-05 12:05:53

iEnumerable 表示“ 对象的收集 s”。因此，在循环内部，您在每次迭代上都会获得对象，实际上您尝试解构对象，而不是 keyvaluepair＆lt; tkey，tvalue＆gt; 。而且您没有适当的解构器对象。

要使用解构，您需要明确和具体类型。为此，您可以：

实现 iEnumerable＆lt; keyvaluepair＆lt; point，Actor＆gt;＆gt;/gt;/ienumerator＆lt; keyvaluepair＆lt; point＆lt; point，Actor，Actor; gt;＆gt;＆gt; for obsoct code> code> blocksheet 。顺便说一句，实现了通用 iEnumerable＆lt; t＆gt; ，您可以通过通用One轻松实现非生成 iEnumerable 。
只需在blocksheet.cast＆lt; keyvaluepair＆lt; point，actor＆gt;＆gt;（））{/*loop hoph body*/} 中使用cast foreach（var（key，val）in blocksheet.cast.cast＆lt; keyvaluepair＆lt; point。但这看起来不是我的最佳选择。

您还可以实现 deconstruct 对象，但是您应该弄清楚它应该如何行为对象，而其他则需要 keyvaluepair ，所以我强烈不建议这样

 公共静态类ext
  {
      公共静态空隙解构（这个对象obj，out a a，out Actor b）
      {
          如果（obj是keyvaluepair＆lt; point，actor＆gt; pair）
          {
              （a，b）=对；
          }
          别的
          {
              a = null;
              b = null;
              //我们可以在这里做什么？
          }
      }
  }

IEnumerable means "collection of Objects". So, inside the loop you got an object on each iteration and you actually try to deconstruct object, not KeyValuePair<TKey, TValue>. And you does not have appropriate deconstructor for the object.

To use a deconstruction, you need explicit and concrete type. To achieve this you can:

implement IEnumerable<KeyValuePair<Point, Actor>>/IEnumerator<KeyValuePair<Point, Actor>> for your object BlockSheet. By the way, having generic IEnumerable<T> implemented, you can easy implement non-generic IEnumerable via the generic one.
just use a cast foreach (var (key,val) in blocksheet.Cast<KeyValuePair<Point, Actor>>()){/*loop body*/}. But this does not looks like a best choice as for me.

you can also implement Deconstruct for Object, but you should figure out how it should behave for objects, other then desired KeyValuePair, so I strongly do not recommend this way

  public static class Ext
  {
      public static void Deconstruct(this Object obj, out Point a, out Actor b)
      {
          if(obj is KeyValuePair<Point, Actor> pair)
          {
              (a,b)=pair;
          }
          else
          {
              a=null;
              b=null;
              // what can we do here?
          }
      }
  }

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