Delphi-具有数据的TClientDataSet的Change Fields定义 [英] Delphi - Change Fields definitions of a TClientDataSet that has data

问题描述

我在运行时为 TClientDataSet 创建 FieldDefs 。仍在运行时，我想删除所有 FieldDefs 。我将 TClientDataSet 物理保存到光盘文件中。我尝试使用以下代码删除现有的 FieldDefs ，以便添加新代码。但这没用：

I'm creating FieldDefs at runtime for a TClientDataSet. Still at runtime I want to remove all FieldDefs. I'm saving TClientDataSet physically to a disc file. I tried removing existing FieldDefs using the following code so I could add new ones. But it didn't work:

with fDataSet do begin
    Active := False;
    DisableControls;
    FieldDefs.Clear;
    Fields.Clear;
    EnableControls;
end;

执行此代码后， FieldDefs 和字段的计数为 0 ，但是如果我关闭并重新打开 disc文件， FieldDefs 和 Fields 仍然存在。

After executing this code, FieldDefs and Fields count are 0, but if I close and reopen the disc file, FieldDefs and Fields are still there.

更改 FieldDefs 和 Fields 的正确方法是什么？

What is the right way to change FieldDefs and Fields?

推荐答案

连续Open从内部数据集重新创建字段。只需清除旧的字段定义，添加新的字段定义并重新创建数据集即可：

Consecutive Open recreates fields from internal Dataset. Just clear old field defs, add new ones and recreated dataset:

...
CDS.FieldDefs.Clear;
CDS.Fields.Add(...);
...
CDS.Fields.Add(...);
CDS.CreateDataSet;
...

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