将数据从数据集结构移动到另一个结构的更快方法(在TDatasetProvider中)

问题描述

限时删除！！

我有一个自定义的TDatasetProvider，它允许为它提供的任何数据创建新字段.

I have an custom TDatasetProvider that allows to create new fields to whatever data it provides.

因此，假设您在原始数据集中找到了以下字段:

So, let's say you got the folowing fields on the original dataset:

• CustomerId
• 名称
• 年龄

您需要使用显示位图在DBGrid上选择它.好吧，因为我的DSP可以添加数据集数据的名为Selected的布尔字段.

And you need to select it on DBGrid using showing an Bitmap. Well, you can since my DSP can addan boolean field called Selected to the dataset data.

我现在的操作方式:

1. 创建2个TClientDataset对象(来源和目标)
2. 在Origin中，我加载了从InternalGetRecords方法的参数获取的数据(覆盖了它)
3. 在Target中，创建从Origin数据集定义的fielddef，并添加开发人员在设计时创建的fielddef.
4. 在目标上执行CreateDataset
5. 然后逐行(逐字段)将数据从Origin数据库复制到Target数据集
6. 最后，将Data变量作为InternalGetRecords的返回值返回.

我真的不知道是否有更优雅(更快)的方式来做到这一点.还有另一种(更快和/或更优雅)的方法来获得结果?

I really don't know if there's a more elegant (and faster) way to do that. There's another (faster and/or elegant) way to get that result?

推荐答案

似乎从源数据集中加载数据后，您可以调用 IDSBase.AddField 来添加更多字段:

It seems that after loading the data from the source dataset, you can call IDSBase.AddField to add more fields:

uses
  DB, DBCommon, DBClient, DSIntf;

type
  THackClientDataSet = class(TClientDataSet);

procedure EncodeFieldDesc(var FieldDesc: DSFLDDesc;
  const Name: string; DataType: TFieldType; Size, Precision: Integer;
  Calculated: Boolean; Attributes: TFieldAttributes);
begin
  // ... copied from TClientDataSet.EncodeFieldDesc
end;

//...
var
  FldDesc: DSFLDDesc;
begin
  FillChar(FldDesc, SizeOf(FldDesc), 0);
  EncodeFieldDesc(FldDesc, 'SELECTED', ftBoolean, 0, 0, False, []);
  with THackClientDataSet(DataSet) do
    Check(DSBase.AddField(@FldDesc));
  // now you can create a second client dataset and assign it DataSet.Data directly:
  // DataSet2.Data := DataSet.Data;
  // DataSet2 now contains the new field (with empty values in all existing records)
end;

我没有对其进行彻底的测试，但是上面的简单示例按预期工作，我能够像往常一样浏览第二个客户端数据集并编辑所有字段的值.

I didn't test it thoroughly but the simple example above worked as expected, I was able to navigate the second client dataset and edit the values of all fields as usual.

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