TDBLookUpComboBox Throws error on Null Opening Value
lazarus / 16-Databases

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jack · 2012-02-20 06:57

I am using the TDBLookUpComboBox as a select box, that is I am only
using the ListSource and not the datasource.  I want to use it to
select values from a db table.

When the control opens, the displayed field is empty, once the user
selects a value, that value appears in the display field and the
keyValue is set.  It seems that either or both of these values are
NULL prior to someone selecting an entry.

If I try to read the selected value from the TDBLookUpComboBox before
it is selected. The control throws an error "Could not Convert varient
type NULL into String.

Since the ListField is a text value, I believe the control should
return an empty string '' and not throw an error.  I am not sure if
fixing the ListField would not just move the problem downstream to the
KeyValue and blow up there.

I could make this work if there were some way to preselect an item in
the list or some way to determine in advance that no selection had yet
been made,  but I cannot find a method to does either of these
things. 

Any Ideas or guidance is greatly appreciated.

Thanks again.

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LuizAmérico · 2012-02-20 11:18

What Lazarus version are you using?

Lookupcontrols have changed a lot since 0.9.30

If you are not using a svn version (0.9.31) yet please try it

Search for lazarus snapshots  in google (or bing whatever)

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jack · 2012-02-20 14:32

Thank you, I will tryLazarus-0.9.31-35502-fpc-2.7.1-20120220-win32.exe

What is a cross-arm-wince-win32.exe?

I see that these are much smaller, is this some sort of add on or a
patch?

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Lacak2 · 2012-02-22 09:57

Quote from: jack on February 20, 2012, 03:32:07 pmWhat is a cross-arm-
wince-win32.exe?

I see that these are much smaller, is this some sort of add on or a
patch?
Adds possibility to your compiler compile under Win32 for ARM/WinCE
target.
So complier produces EXE, which can be run on ARM CPU with WinCE OS
(and can not run on I386/Win32)