检查是否在TClientDataset中更改了行 [英] Check if row was changed in a TClientDataset

问题描述

我有一个带有n个字段的TClientDataset，我必须遍历它们以计算有多少已更改但正在执行:

I have a TClientDataset with n fields and I have to loop through them to count how many have changed but doing:

if (Cds.fields1.Value <> Cds.fields1.OldValue) and (Cds.fields2.Value <> Cds.fields2.OldValue) etc....

或通过Cds.fields [I]循环不是很干净"

or looping through Cds.fields[I] is not very 'clean'

有Cds.RowChanged方法吗?

Is there a Cds.RowChanged method or something?

推荐答案

您可以为此使用TClientDataSet的UpdateStatus属性:

You can use the TClientDataSet's UpdateStatus property for this:

if Cds.UpdateStatus = usModified then
  //  current row was changed

其他可能的值是usUnmodified，usInserted和usDeleted.与TDataSet.Modified属性不同，当前行的UpdateStatus在其更改已由CDS.Post发布回CDS之后仍然存在.显然，由您决定应用程序需要这些数字值中的哪一个.

Other possible values are usUnmodified, usInserted and usDeleted. Unlike the TDataSet.Modified property, the UpdateStatus for the current row persists after its change(s) have been posted back to the CDS by CDS.Post. Obviously, it's up to you which of these number values you need for your application.

如联机帮助中所述，您可以使用UpdateStatus设置计算字段的值:

As noted in the Online Help, you can use the UpdateStatus to set the value of a calculated field:

procedure TForm1.ClientDataSet1CalcFields(DataSet: TDataSet);
begin
  case TClientDataSet(DataSet).UpdateStatus of
    usUnmodified: FieldByName('Status').AsString := '';
    usModified: FieldByName('Status').AsString := 'M';
    usInserted: FieldByName('Status').AsString := 'I';
    usDeleted: FieldByName('Status').AsString := 'D';
  end;
end;

您还可以使用其StatusFilter属性临时过滤TClientDataSet以选择具有特定UpdateStatus的行:

You can also use its StatusFilter property to temporarily filter a TClientDataSet to select rows with a specfic UpdateStatus:

procedure TCDSForm.Button1Click(Sender: TObject);
begin
  if CDS.StatusFilter = [] then
    CDS.StatusFilter := [usModified]
  else
    CDS.StatusFilter := [];
  Caption := IntToStr(CDS.RecordCount);
end;

请注意，将StatusFilter设置为usModified的CDS.RecordCount不一定返回与CDS.ChangeCount属性相同的值，因为ChangeCount值包括已插入的行数>以及已修改的号码.

Note that CDS.RecordCount with the StatusFilter set to usModified does not necessarily return the same value as the CDS.ChangeCount property, because the ChangeCount value includes the number of rows inserted as well as the number that have been modified.

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