在com+数据对象中,用巢状数据表实现Master/Detail表,想要在Detail表中加入Calculated字段,如何实现?

Question

在com+数据对象中,有adsmaster(master表), adscalmaster(calmaster表),adsdetail(detail表),adscaldetail(caldetail表)四个数据控件;
master表中的Calculated字段calfieldmaster取自calmaster表;
detail表中的Calculated字段calfielddetail取自caldetail表;
adsmaster和adsdetail已设定成巢状数据表,adscalmaster及adscaldetail都有相关设定;
adsmaster之oncalcfields编写以下程序以取值:
try
adscalmaster.parameters.parambyname(‘calfieldmastid’).value := dataset.fieldbyname(‘masterid’).value;
adscalmaster.active:=true;
dataset.fieldbyname(‘calfieldmaster’).value:=adscalmaster.fieldbyname(‘calfield’).value;
finally
  adscalmaster.active:=false;
end;adsdetail之oncalcfields编写以下程序以取值:
try
adscaldetail.parameters.parambyname(‘calfielddetailid’).value := dataset.fieldbyname(‘detailid’).value;
adscaldetail.active:=true;
dataset.fieldbyname(‘calfielddetail’).value:=adscaldetail.fieldbyname(‘calfield’).value;
finally
  adscaldetail.active:=false;
end;前端用clientdataset连接时产生”非法参数”的错误,如何解决?

Answer 1

在ClientDataSet里加个字段是计算类型的，然后
/CdsCont_Appbill_List_goods：cilentDataSet的计算事件里
procedure TContAppFrm.CdsCont_Appbill_List_goodsCalcFields(
  DataSet: TDataSet);
var
  sql, SQL_BASE: string;
  dest_id:Integer;
  A: Array [0..0] of string;
  b: boolean;
begin
  inherited;
  if (DataSet.FieldByName('GOOD_ID').IsNull) then
    Exit;
  dest_id:=DataSet.FieldByName('GOOD_ID').AsInteger;
  if (dest_id=0) then
    Exit;
  begin
    cdsLookUp.Active := False;//cdsLookUp：临时的ClientDataSet
    SQL_BASE := 'select GOOD_ID, GOOD_NAME FROM GOODS';
    sql := SQL_BASE + ' where GOOD_ID = '+ IntToStr(dest_id);
    cdsLookUp.Data := MyDBPool.QueryRecord(sql);
    if cdsLookUp.RecordCount <> 0 then
    begin
      cdsLookUp.First;
      DataSet['GOOD_NAME']:=cdsLookUp['GOOD_NAME'];
    end;
  end;
end;