Problem with TwwDBComboBox not showing similar Items in Delphi (InfoPower2012)

[Paul Ross]

Using InfoPower 2012 (Oct2012) with Delphi XE2.

 

I've placed a TwwDBCombobox on a form. I'm using it without a DB connection and have added items manually (see attached image). I want the displayed value to be the person's first name, but the stored data is a payroll number. Although the stored payroll values are unique, it's possible that some people will have the same first name. For example, David and Paul are listed twice with different payroll numbers in this example.

 

The problem is that when 'Map Displayed Value' is turned on, the drop-down list shows the payroll number for the first 'Paul' against each instance of 'Paul'. The other Paul with payroll 18 isn't listed (see bottom left of attached image).

 

Am I missing something?

 

[Roy Woll]

The TwwDBComboBox requires that the display value be unique. It does not support the mode you are using. I suggest using the TwwDBLookupCombo instead for this as it is more capable in this situation. If you don't want to have to create a physical dataset, you don't have to as you can create an in-memory dataset for this.  For instance drop in a TwwDBLookupCombo and TwwClientDataSet and set the fielddefs to the fieldnames that you want, or copy the following text to the clipboard and paste it into your form to create the in-memory dataset. 

object ClientDataSet2: TClientDataSet

  Active = True

  Aggregates = <>

  FieldDefs = <

    item

      Name = 'Description'

      DataType = ftString

      Size = 20

    end

    item

      Name = 'Code'

      DataType = ftInteger

    end>

  IndexDefs = <>

  Params = <>

  StoreDefs = True

  Left = 296

  Top = 88

  Data = {

    600000009619E0BD010000001800000002000000000003000000600014436C69

    656E7444617461536574324669656C6431010049000000010005574944544802

    000200140014436C69656E7444617461536574324669656C6432040001000000

    00000000}

end

The set your lookupfield to code and lookuptable to your newly created clientdataset.  Finally the only remaining step is to initialize the data in your form's OnShow event. For instance....

procedure TComboDemoForm.FormShow(Sender: TObject);

begin

  clientdataset2.Insert;

  clientdataset2.fieldbyname('description').AsString:= 'David';

  clientdataset2.fieldbyname('code').AsString:= '12';

  clientdataset2.post;

  clientdataset2.Insert;

  clientdataset2.fieldbyname('description').AsString:= 'David';

  clientdataset2.fieldbyname('code').AsString:= '14';

  clientdataset2.Post;

  clientdataset2.Insert;

  clientdataset2.fieldbyname('description').AsString:= 'Paul';

  clientdataset2.fieldbyname('code').AsString:= '16';

  clientdataset2.Post;

  clientdataset2.Insert;

  clientdataset2.fieldbyname('description').AsString:= 'John';

  clientdataset2.fieldbyname('code').AsString:= '17';

  clientdataset2.Post;

  clientdataset2.Insert;

  clientdataset2.fieldbyname('description').AsString:= 'Paul';

  clientdataset2.fieldbyname('code').AsString:= '18';

  clientdataset2.Post;

end;

-Roy