Using TDBLookupCombo correctly?
lazarus / 16-Databases

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bill0287 · 2013-12-01 06:28

I have just found Lazarus after being out of Delphi for many years. I
need to update an old app and I am having trouble translating some
code.

I have a TDBLookupComboBox looking up a field value in a "look up"
table (Dbf). I need to go to that record and then take two other field
values from that record and apply them to DBEDit fields attached to a
second database.

I don't know how to get the lookup table to set to the right record
based on the combo's value?
I don't know how to capture the two other fields and apply them to the
second database via the dbedits so that it updates the table?

In Delphi I had something like this, but can't seem to figure out how
to do this in Laz:

Code: [Select]  //Use dblookupcombo to find name in data.dbf
  Table3.SetKey;
  Table3.FieldbyName('NAME').AsString := DBLookupComboBox.Text;
  Table3.GotoKey;
  //Table1.Edit;
  DBEdit1.Text := Table3.FieldbyName('A').AsString;
  DBEdit2.Text := Table3.FieldbyName('B').AsString;

Any help would be appreciated

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BigChimp · 2013-12-01 09:17

Not a GUI guy at all, but: could you use the ListSource to get the
lookup datasource and from there get the field contents?

http://wiki.lazarus.freepascal.org/dblookupcombobox
combined with
http://lazarus-
ccr.sourceforge.net/docs/lcl/dbctrls/tdblookupcombobox.html

Alternatively, apparently this control
http://wiki.lazarus.freepascal.org/dblookupcombobox#Alternative_contro
l
allows displaying multiple fields in the lookup table. Perhaps you can
set their column widths to 0, hiding them, but still making the values
available for retrieval.

Hope somebody who actually knows what he's doing/has done this before
will step in - and ideally update that tdblookupcombobox wiki page

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mangakissa · 2013-12-01 09:26

Setkey is only working with an index.
Use locate to find your record.
Code: [Select]if
Table3.locate('name',vararrayof([DBLookupComboBox.Text]),[]) then
begin
  DBEdit1.Text := Table3.FieldbyName('A').AsString;
  DBEdit2.Text := Table3.FieldbyName('B').AsString;
end;

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bill0287 · 2013-12-01 16:36

Thanks. I was able to use locate to find and copy the records I
needed. I noticed one other issue:

I need the found value of the DBLookupCombo box to be written to the
database, which it was, but when I run the program again, the
DBLookupCombo box field is blank and not showing the value I selected
(but the data is in the table).

I have it set up like this:

note that the lookup DB and the target DB are the same actual table
but with different datasource/dbf components.

DBLookupComboBox:

ListSource = LookupDatasource
DataSet = LookupDataset
ListField and Keyfield = Name

DataSource = the primary Datasource
DataField = the target field for the lookup value

I guess my question is why does the DBLookupCombo box not display the
value found in it's Datafield?

Maybe I am doing this wrong

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mangakissa · 2013-12-02 12:47

You can't use a dataset twice for lookup and data. That's looking for
trouble and isn't the right way.
A lookuptable is a dataset from another table with the key of the
requested field kan be found.
Just copy your fields to a memdataset if you want to use the primary
dataset.

lookupdataset = memtable