How to use a TcxCustomDataSource in a TcxExtLookupComboBox? - delphi

Question

I use a TcxExtLookupComboBox from Devexpress and try to implement a custom datasource. I have set the customdatasource like this:
procedure TMainForm.FormCreate(Sender: TObject);
begin
fDataSource := TMyDataSource.Create;
cbotestSearch.Properties.View.DataController.CustomDataSource := fDataSource;
end;
TMyDataSource is defined here:
unit Datasource;
interface
uses
Classes,
IBQuery,
SysUtils,
cxCustomData;
type
TSearchItem = class
private
BoldID: String;
Display: String
end;
TMyDataSource = class(TcxCustomDataSource)
private
fSearchList: TList;
protected
function GetRecordCount: Integer; override;
function GetValue(ARecordHandle: TcxDataRecordHandle; AItemHandle: TcxDataItemHandle): Variant; override;
public
constructor Create;
destructor Destroy; override;
procedure GetData;
end;
implementation
constructor TMyDataSource.Create;
begin
inherited Create;
fSearchList := TList.Create;
end;
destructor TMyDataSource.Destroy;
begin
FreeAndNil(fSearchList);
inherited;
end;
procedure TMyDataSource.GetData;
var
vItem: TSearchItem;
begin
fSearchList.Clear;
vItem := TSearchItem.Create;
vItem.BoldID := '1000';
vItem.Display := 'test';
fSearchList.Add(vItem);
vItem := TSearchItem.Create;
vItem.BoldID := '1100';
vItem.Display := 'test2';
fSearchList.Add(vItem);
DataChanged; // Don't do anything as provider is nil
end;
function TMyDataSource.GetRecordCount: Integer;
begin
// Is never entered
Result := fSearchList.Count;
end;
function TMyDataSource.GetValue(ARecordHandle: TcxDataRecordHandle;
AItemHandle: TcxDataItemHandle): Variant;
begin
// Is never entered
Result := 'Test';
end;
end.
The problem is that TMyDataSource.GetValue is never called. Any hint how to fix ?
Update 1: I have another hint here. If I single step in the DataChanged method that should cause GetValue to be called is looks like this:
procedure TcxCustomDataSource.DataChanged;
begin
if Provider = nil then Exit;
// Code using Provider
end;
and Provider is nil in this case. But I have assigned the Datasource in Forms oncreate as you see.

Answer 1

cxExtLookupComboBox can only work with DB~views. Such views cannot accept instances of the TcxCustomDataSource object as a DataSource. So, your code will not work :-(. There is a suggestion to implement this feature in the future and it is registered at:
http://www.devexpress.com/Support/Center/ViewIssue.aspx?issueid=AS10025