TStrings and comma-separated text
By Mark G. Wiseman

Conversion functions
Figure A shows our example program. On the right is a TMemo control containing plain text. On the left is a TMemo control with the same text converted to comma-separated text. This entire program is driven by the two simple functions, ConvertToCommSep() and ConvertFromCommaSep(), as shown in Listing A and B.

Figure A: Our example program displays plain text and comma-separated text.

Listing A: Function to convert text to comma-separated text

void ConvertToCommaSep(TStrings *source,
   TStrings *dest, int itemsPerRecord)
   {
   if ((source->Count % itemsPerRecord) != 0)
      throw EConvertError(
             "Wrong number of items per record");

   int recordCount = source->Count /
      itemsPerRecord;

   TStringList *temp = new TStringList;
   for (int i = 0; i < recordCount; i++)
      {
      for (int j = 0; j < itemsPerRecord; j++)
      temp->Add(source->Strings[i *
      itemsPerRecord + j]);

      dest->Add(temp->CommaText);
      temp->Clear();
      }

   delete temp;
   }

Listing B: Function to convert back from comma-separated text

void ConvertFromCommaSep(Tstrings
   *source, TStrings *dest)
   {
   dest->CommaText = source->Text;
   }

Both functions take arguments for two pointers to objects derived from TStrings. These pointers point to a source and destination for the conversion. ConvertToCommSep() also takes an argument--itemsPerRecord--that specifies the number of items to put on each line (record) of comma-separated text.

ConvertFromCommaSep() really requires no explanation. It derives all its functionality from the CommaText property of TStrings.

ConvertToCommaSep() is only slightly more complicated. ConvertToCommaSep() first checks to see if the number of items to be converted is a multiple of itemsPerRecord. If it isn't, an exception is thrown. Next, ConvertToCommaSep() creates a temporary TStringList object to use while building records with the correct number of items.

ConvertToCommaSep() iterates through the source text, adding itemsPerRecord items to the temporary TStringList. Once a record contains the correct number of items, it's added to the destination TStrings object using the CommaText property of the temporary TStringList. This is the point at which the actual conversion takes place. Listing C shows how easily we use these two functions in our example application to perform the conversion in either direction.

Listing C: Using the conversion functions

void __fastcall TMainForm::ConvertFromButtonClick(
   TObject *Sender)
   {
   ConvertFromCommaSep(Memo1->Lines,
      Memo2->Lines);
   }

void __fastcall TMainForm::ConverToButtonClick(
   TObject *Sender)
   {
   Memo1->Lines->Clear();

   ConvertToCommaSep(Memo2->Lines, Memo1->Lines,
      IPREdit->Lines->Text.ToInt());
   }

As we comma-separate
You could write complicated parsing code to convert to and from comma-separate text. Or, you could use the Borland Database Engine. Either method would work, but either of these methods would cost you a lot of time and effort. The CommaText property of TStrings comes to the rescue with a minimum of fuss and muss. As usual, the VCL provides a simple, elegant solution to a common programming problem.