Problem Using the TIWComboBox

Hi everyone, I'm not sure where I should exactly put this post, so I will probably try a couple of places. 

Anyway, I am new to the intraweb.  I am using Delphi2006 and want to convert a system i had created to the intraweb.  I have no problem when using the regular combo box, but I'm trying to use the TIWComboBox and having a horrible time to get it to work!

It will not clear and I've thought I've tried everything.  I can't get it to retrieve the information from the database unless I use:

 IWCombobox.NoSelectionText         := UserSession.DS.Fields[1].AsString;

I cannot find alot of information on NoSelectionText.  Even then, it seems that this doesn't work all of the time and I don't know why.   I'm totally confused on this component and hope someone can help.  I've wasted too much time on this.  Can anyone even suggest a good site that would help?

Any help is greatly appreciated!  Thanks!!

Hi Marge,

First thing I should say is that I'm not an IW user. (I have nothing against it, just haven't gotten around to using it).

I checked IW help for the vesion that ships Delphi 7 (I didn't install IW with my D2006).  It looks like two IW components will behave pretty much (but not exatly) like their VCL counterparts.

TIWComboBox  has an Items property.  I think this is what's going to interest you.

To clear the combobox, try:

MyComboBox.Items.Clear;

To populate the combobox try:

MyComboBox.Items.Add('stringValue);

Performance tip:  After clearing, and before populating, set the Sorted property False.  Add your items, and, when finished, set Sorted to True.

Forcing an items list (TStrings) to sort while inserting (Sorted := True) is expensive in terms of machine cycles.  Every addition forces the TStrings to resort themselves.

Saving the sort operation for last means the Items list has to sort itself only once.  You'd be amazed at the difference in performance when the number of items is large.

DB Tip #1: When populating a ComboBox from a database, it's often useful to store not only the item name, but also its primary key value.  This is frequently an autoinc (integer) value.  If it is, I use this trick:

MyComboBox.Items.AddObject('ItemName', Pointer(PKvalue));

The Object property of lists (TStrings) holds a pointer, whis is the reason for the cast, above).

To retrieve the primary key, you do the revese cast: Integer(object);

DB Tip #2: Have you looked at TIWDBComboBox? It appears to be analagous to the VCL TDBComboBox, complete with properties for DataSource and Field. It might actually be easier to use - and save you some manual coding.

If the above doesn't help, there are at least two potentially useful resources:

http://www.tamaracka.com

Tamarack is the maker of the Rubicon add-on for full-text indexing databases  At the URL, above, they maintain an archive of Borland (and related 3rd party) newsgroup posts - as a way to show off Rubicon.

I just did a search, there, on "TIWComboBox," and it returned 170 articles!

You don't mention whether you're using the bundled version of IntraWeb, or the full-blown commecial one.  If the latter, you're entitled to some support from Atozed, makers of IntraWeb.

If the bundled version, well, support is limited to FAQs on the Atozed site, and Atozed newsgroups and Chat.

See "Peer Support," here:

http://www.atozed.com/IntraWeb/Support/Peer.EN.aspx

Hope that helps.

Wes Peterson
Senior Software Engineer
Prestwood IT Solutions
http://www.prestwood.com

Thank you so much for your help!  What I ended up doing was this:

 IWCombobox.NoSelectionText         := '';
 IWCombobox.Items.Text                   := IWCombobox.NoSelectionText;
 IWCombobox.Clear;
Load_Codes;

Load_Codes consists of this coding:

 IWCombobox.Items.Clear;
 UserSession.DS.Close;
 UserSession.DS.SQL.Clear;
 UserSession.DS.SQL.Add( 'Select Distinct(Code), Sub_Code, Description From BC_CODE' );
 UserSession.DS.SQL.Add( 'Order by Code' );
 UserSession.DS.Open;
 Count     := UserSession.DS.CountQueryHits;
 SetLength(Array,Count);
 UserSession.DS.First;
 For I := 0 To Count - 1 Do
 Begin
         Array[I] := UserSession.DSCode.AsString +' '+ UserSession.DSSub_Code.AsString +' '+
                             UserSession.DSDescription.AsString;
         IWCombobox.Items.Add(Array[I]);
         UserSession.DS.Next;
      End;
      UserSession.DS.Close;

Why I had to put in those 3 lines up above in order to clear the combo box is beyond me.  I thought that was crazy.  I was doing trial and error and finally got the box to clear using that code.

I will look into the http://www.tamaracka.com site further.   Thanks!!