delphi Delphi_如何在Delphi中用代码来完成计算字段的创建 |笨鱼技术网

procedure TForm1.FormCreate(Sender: TObject);
var
  NewField:TField;
  i:integer;
begin
//表中有两字段SName,Birth，现在我们动态生成一个计算字段Age，显示出年龄
  NewField:=TStringField.Create(ADOTable);
  //创建一个TStringField类型的字段
  ADOTable.Close;
  for i:=0 to ADOTable.Fields.Count-1 do
    ADOTable.Fields[0].Free;//释放所有的静态字段
  for i:=0 to ADOTable.FieldDefs.Count-1 do
    ADOTable.FieldDefs.Items[i].CreateField(ADOTable);
//根据FieldDefs的字段信息动态的生成静态字段
  NewField.Size:=5;
  NewField.FieldName:=Age;
  NewField.FieldKind:=fkCalculated;
//设置这个这字段为计算字段
  NewField.DataSet:=ADOTable;
//把这个字段加到ADOTable上
  ADOTable.Open;
end;

procedure TForm1.ADOTableCalcFields(DataSet: TDataSet);
var
  YY1,YY2,MM,DD:Word;
  TmpDate:TDate;
begin
  DecodeDate(Date,YY1,MM,DD);
  TmpDate:=DataSet.FieldByName(Birth).AsDateTime;
  DecodeDate(TmpDate,YY2,MM,DD);
  DataSet.FieldByName(Age).AsString:=IntToStr(YY1-YY2)+岁;
  //在OnCalField中显示出年龄
end;