Refresh after commit
lazarus / 16-Databases

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fpcoder · 2015-10-22 17:53

A DBLookupListBox shows the names of items in a table. If a record is
added, the wrong name comes up in associated DBAware controls. I have
the ListSource, ListField and KeyField filled out and DataSource and
DataField left empty.

There is an sampleproject added, with a small sqlite database with it.

To edit the properties of an item, double-click it and a form called
frmItem is called up. It has only a DBEdit that shows the name and you
can edit it and click OK to save.

For the DBEdit to show the right value ScrollListDataSet is set to
true in the query, meaning that when the frmItem form shows up, it
shows the values of the record that was selected in the
DBLookupListBox of the main form.

So far so good, but as I said, when a new record is added and you
double-click it in the listbox the DBEdit shows the name of an earlier
item.

Calling close and then open on the dataset makes the new record show
correctly, but why isn't Refresh enough?

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i qryItems.Po
st;qryItems.ApplyUpdates;TX.CommitRetaining;qryItems.Refresh;
Also, if an item is double-clicked and then saved, why are there so
many calls to the datasource OnDataChange? (See log window of sampel
app)

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balazsszekely · 2015-10-22 20:31

You need to provide a DataSource and a DataField. The DBLookupListBox
represents a field in one table by displaying the value of a
corresponding field in another table. In your case there is only one
table(Items) no need for DBLookupListBox.

Another good practice after Refresh:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i  ID := qryI
tems.FieldByName('item_id').AsInteger; qryItems.Post; qryItems.Refresh
; if not qryItems.Locate('item_id', ID, []) then      
ShowMessage('somethings went wrong');

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fpcoder · 2015-10-22 22:26

@GetMem: Thanks for Locate suggestion. But you suggest the DBListBox
instead? That box has to be manually populated. I used DBLookUpListBox
because it loads the records automaticly. Dont you think this is a
valid way of using it?

The goal of this exercise is to find the most efficient way of adding
items and editing their properties. Maximum RAD with the least code.
The idea is like this: By selecting an item in the ListBox, the
current record is changed. Selecting an item in the ListBox should not
change any column value anywhere, it should just move the cursor to a
new record. Thats why DataSource and DataField are left empty and only
ListSource is used. And when the "property editor" is brought up
(frmItem) it displays the name of the current item without a line of
code. It works only if ScrollListDataSet is true. A snag though, that
the table has to be closed and opened for newly added items to show
correctly. I hoped there was some fix. With Zeos there is no need to
close and open.

This was the best I could come up with, but I'm all ears what approach
you guys use.

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balazsszekely · 2015-10-23 04:06

QuoteThanks for Locate suggestion.You're welcome!

QuoteBut you suggest the DBListBox instead? That box has to be
manually populated. I used DBLookUpListBox because it loads the
records automaticly. Dont you think this is a valid way of using it?
The use of TDBListBox and TDBLookupListBox is a little bit counter
intuitive. It was designed for entirely other purposes then you would
expect. You should switch to TDBGrid.

QuoteThe goal of this exercise is to find the most efficient way of
adding items and editing their properties. Maximum RAD with the least
code. Just replace the listbox with a grid. Hide column
items_id(usually the id is not displayed in the grid). Add the locate
stuff, remove some unnecessary lines like:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i   if
lbItems.Count < 1 then Exit;  if lbItems.ItemIndex > -1 then That's
it. It should work.