Question

A DataSet hooked to a grid has:

TField.DisplayFormat := '$######.00'

I want to build list of strings that are in a particular column of my grid with:

while NOT DataSet.EOF do
   StringList.Add(TField.DisplayText);

I had hoped for speed to do:

DataSet.DisableControls;

but this also disables the application of the DisplayFormat.

Not disabling the controls means this runs quite slowly (in the archaic, deprecated, “You should abandon it now“-Paradox/BDE.)

So, my question:

Is there a formatting function (say, DFFormat) that uses the same notation as TField.DisplayFormat?

Then I could do:

 DataSet.DisableControls;
 while NOT DataSet.EOF do
   StringList.Add(DFFormat(TField.Value));

Or, since there are only have a few data types, so I could do the code below and figure out ways to create a Format string that works:

 DataSet.DisableControls;
 while NOT DataSet.EOF do
   begin
     if TField.FieldType = ftString
        StringList.Add(AsString)     
     else if TField.FieldType = ftFloat then
        StringList.Add(Format(TField.Value, ...)
     else...

The code above wouldn’t be much longer than shown, but I’m hoping there is a formatting function that uses TField’s DisplayFormat. Or am I asking too much?

Answer 1

DisplayFormat only applies to four TField descendants (TAggregateField, TDateTimeField, TNumericField, and TSQLTimeStampField). It seems to me this would be very easy to implement for three of them:

function TFieldToDisplayFormat(const Fld: TField): string;
begin
  Result := Fld.AsString;
  if (Fld is TDateTimeField) then
    Result := FormatDateTime(TDateTimeField(Fld).DisplayFormat,
      TDateTimeField(Fld).AsDateTime)
  else if (Fld is TNumericField) then
    Result := FormatFloat(TNumericField(Fld).DisplayFormat,
      TNumericField(Fld).AsFloat)
  else if (Fld is TSQLTimeStampField) then
    Result := SQLTimeStampToString(TSQLTimeStampField(Fld).DisplayFormat,
       TSQLTimeStampField(Fld).AsSQLTimeStamp);
end;

// Sample use
while not DataSet.Eof do
  SL.Add(TFieldToDisplayFormat(WhatEverField));