[fpc-pascal] Suggestion: TDataSetEnumerator

[silvioprog]

On Tue, Mar 10, 2015 at 5:48 PM, silvioprog <silvioprog at gmail.com> wrote:

> On Sat, Mar 7, 2015 at 4:27 AM, LacaK <lacak at zoznam.sk> wrote:
>
>> What if TDataSetEnumerator.Current will return TFields instead of
>> TDataSet which enumerates?
>>
>> Example:
>>   procedure IterateDataSet;
>>   var DataSet, DS: TDataSet;
>>       Flds: TFields;
>>       F: TField;
>>   begin
>>     for Flds in DataSet do
>>       for F in Flds do  // DataSet can be still accessed by Flds.DataSet
>>         writeln(F.AsString,'|');
>>   end;
>>
>> I know that it is more or less same ... it depends what will be most
>> common usage scenario.
>> In one case it will be better have DataSet in another Fields.
>> When iterating DataSet IMO only Fields, Recno, Bookmark are usable
>> properties which changes on each itteration and can be practically used
>> inside loop.
>> But I think, that most common scenario will be use only Fields inside
>> loop.
>> In both cases user must define "control variable" either of TDataSet type
>> or TFields type.
>>
>> (*** Example implementation ***)
>> type
>>   TDataSetEnumerator = class
>>     private
>>       FDataSet: TDataSet;
>>       FBOF: Boolean;
>>       function GetCurrent: TFields;
>>     public
>>     &nb sp; constructor Create(ADataSet: TDataSet);
>>       function MoveNext: Boolean;
>>       property Current: TFields read GetCurrent;
>>   end;
>>
>> operator Enumerator(ADataSet: TDataSet): TDataSetEnumerator;
>> begin
>>   Result := TDataSetEnumerator.Create(ADataSet);
>> end;
>>
>> constructor TDataSetEnumerator.Create(ADataSet: TDataSet);
>> begin
>>   inherited Create;
>>   FDataSet := ADataSet;
>>   FBOF := True;
>>   FDataSet.First;
>> end;
>>
>> function TDataSetEnumerator.GetCurrent: TFields;
>> begin
>>   Result := FDataSet.Fields;
>> end;
>>
>> function TDataSetEnumerator.MoveNext: Boolean;
>> begin
>>   if FBOF then
>>     FBOF := False
>>   else
>>     FDataSet.Next;
>>   Result := not FDataSet.EOF;
>> end;
>>
>> (* *** *)
>>
>> -Laco.
>>
>
> Very nice. I open a new issue about that (
> http://bugs.freepascal.org/view.php?id=27644). =)
>
> I have a question. Can I use two or more enum operators in a same unit?
>

It was applied in trunk. Thanks guys! (y)

-- 
Silvio Clécio
My public projects - github.com/silvioprog
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