If I understand you correctly, you want to use a DBLookupComboBox. You have to supply values for the following properties
- datasource - linked to the table which you are editing, presumably 'items'
- datafield - the name of the field in the table which you are editing, presumably 'item_type'
- listsource - linked to the table which populated the combobox, presumably 'item_types'
- list field - the name of the field from 'item_types' which you want to display, presumably 'name'
- key field - the name of the field from 'item_types' which will be inserted into the items record, presumably 'item_type'
The table which populated the combobox is never edited.
You can validate the values before posting the new/edited 'items' record.
I can show you how to use a non-data aware combobox if necessary, but it's easier to use the data aware version.
Regarding validation, I use the following code template in edit dialogs.
Function TEditQuestion.Execute (n: longint): boolean;
var
gen: longint;
begin
sdsEditQuestion.params[0].asinteger:= n; // TSQLDataSet
with qEditQuestion do // TClientDataSet
begin
open;
if n = -1 then // new record
begin
caption:= 'New record';
insert;
fieldbyname ('alive').asinteger:= 1;
// initialise necessary fields in the dataset
end
else caption:= 'Editing record ' + inttostr (n);
edit;
if showmodal = mrOK then
begin
// validation code comes here. Set 'result' to true if everything is ok
if result then
begin
if n = -1 then
begin
with qGenID do
begin
open;
gen:= fields[0].asinteger; // get new value from generator
close
end;
FieldByName ('id').asinteger:= gen;
end;
post;
applyupdates (0)
end
else cancel // showmodal = OK, result = false
else // showmodal cancelled
begin
cancel;
result:= false
end;
end // with qEditQuestion
end;