Delphi：如何使用TObjectList< T>？

问题描述

我需要了解如何使用通用Delphi 2009 TObjectList 。我的非 TObjectList 尝试看起来像

I need to understand how to use the generic Delphi 2009 TObjectList. My non-TObjectList attempt looked like

TSomeClass = class(TObject)
private
  FList1: Array of TList1;
  FList2: Array of TList2;
public
  procedure FillArray(var List: Array of TList1; Source: TSource); Overload;
  procedure FillArray(var List: Array of TList2; Source: TSource); Overload;
end;

这里， TList1 和 TList2 继承相同的构造函数构造函数TParent.Create（Key：string; Value：string）; 。然而，由于不同的专业化（例如不同的专用领域），它们将不是相同的类型。所以我必须写两个几乎相同的填充方法：

Here, TList1 and TList2 inherits the same constructor constructor TParent.Create(Key: string; Value: string);. However, due to different specialization (e.g. different private fields), they will not be of the same type. So I have to write two nearly identical fill methods:

procedure TSomeClass.FillArray(var List: Array of TList1; Source: TSource);
begin
  for i := 0 to Source.List1.Count - 1 do begin
    SetLength(List, Length(List) + 1);
    List[i] := TList1.Create(Source.List1[i].Key, Source.List1[i].Value);
  end;
end;

与 FillArray（List：TList2的数组;源：TSource）; 是完全相同的，除了用 TList2 替换 TList1 。据我所知，这可以通过使用 TObjectList 和单个填充方法整齐地规避;但是，我不知道如何去做这个。有人有一些很好的指点吗？谢谢！

with FillArray(List: Array of TList2; Source: TSource); being identical, except for the replacement of TList1 with TList2 throughout. As far as I understand, this could be neatly circumvented by using TObjectList and a single fill method; yet, I don't have a clue how to go about this. Do anyone have some good pointers on this? Thanks!

推荐答案

您将无法通过使用通用列表来缩减，因为通用类型是类定义。因此，一个 TObjectList< TMyClass1> 与 TObjectList< TMyClass2> 不同（并且不兼容）。使用通用列表超过正常TList / TObjectList的主要好处是改进了类型安全性，较少的转换和更清晰的代码。

You wouldn't be able to condense that down by using a generic list, since a generic's type is part of the class definition. So a TObjectList<TMyClass1> is different from (and incompatible with) a TObjectList<TMyClass2>. The main benefit of using generic lists over normal TList/TObjectList is improved type safety, with less casts and cleaner code.

此外，如果您使用键/值对，你把它们放在列表中，然后通过搜索一个键并返回相关的值来检索它们？如果是这样的话，可以看一下在Genericics.Collections中的TDictionary。它是一个通用的键/值哈希表，可以为您大大简化此过程。

Also, if you're using key/value pairs, are you putting them into a list and then retrieving them by searching for a key and returning the associated value? If so, take a look at TDictionary in Generics.Collections. It's a generic key/value hash table that will greatly simplify this process for you.

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