How to set DefaultSelectedItems for multiple select combo box based on a choice field in a gallery

[gabrielaurora]

I have a gallery that returns multiple rows. The gallery's datasource is a Collection based on a table that has a column of datatype = Choice with multiple select allowed.

I have multiple pages in my app with Back and Next buttons. 

When I select choices in the combo box it patches correctly, but if I click Next and go to the next page, and then click Back to go back to the page with the gallery, the values in the multiple select combo box are blank/cleared. Same also happens if I open the form from the beginning and it needs to return the multiple selected values for the gallery.

Setting DefaultSelectedItems = ThisItem.Blah doesn't work as it seems to return the value of the selected row (usually the last row) for all rows. (Is this a bug as the same doesn't happen for any other control type?) 

I think I need a way to loop through gallery rows and set the value manually. I've tried looping through the gallery but I'm not sure if I did it correctly but also I'm not sure where to do it. Screen OnVisible seems to run before DefaultedSelectedItems so I can't use that.

In summary, I need help on populating the DefaultSelectedItem of a multiple select combo box in a Gallery. Thanks.

[BCBuizer]

Hi @gabrielaurora,

What exactly is being patched when making changes in the selection?

If it is the table on which the collection in based, do you make sure to also update the collection?

In case it is the collection, could it be that the collection is being populated in the OnVisible property of the screen, basically overwriting the changes that were made?

For any scenario I would consider if a collection is really needed since it can cause the described issues. It may be better to connect directly to your table.

[gabrielaurora]

Thanks for the reply. I originally did base it on the table but got this issue and found a suggestion to use a collection in galleries as they are more stable, but the issue still happened either way.

I actually didn't explain myself correctly in the original post. I said that when I go back to the page the values are clear/blank but that's not correct.

If I set DefaultSelectedItems to ThisItem.Blah (as your meant to) when I patch the data and the gallery is refreshed (this is done automatically, I don't do a refresh) or move to a different page then come back, the values are set to the values of the last row.

For example, say I have 2 rows and I set the multiple select to A and B in the first row and C and D in the second row, after patching or moving page and coming back, the multiple select for both rows are C and D, even though the data patched correctly and the database shows A and B for the first row and C and D for the second. So to me setting DefaultSelectedItems to ThisItem.Blah is not working correctly, and this is my main issue.

It's just an issue for the multiple select combobox as I have other controls in the gallery with DefaultSelectedItems = ThisItem.Blah that all work fine. I've tried the same field in a Form and it works fine, it just has a problem in a Gallery.

I have googled extensively and cannot find a single example of multiselect in a gallery so I'm beginning to think it can't be done.

[BCBuizer]

Hi @gabrielaurora ,

I think the issue may be in a misunderstanding of how collections work:

They are very similar to variables, meaning they keep their value from the moment you set them until you make a change to them. In your case I don't think you are updating your collection after you have updated your data source. This means that when you navigate to another screen and back, the gallery will reset and the (non updated) values from the collection are displayed.

To resolve this, you will need to update your collection after making changes to the data source or get rid of using the collection altogether. 

[gabrielaurora]

Thanks again for the reply.

Ok, I've been working late nights on this and have been trying many things and the actual issue is slightly different to my previous posts (again... 😬) I removed DefaultSelectedItems = ThisItem.Blah for testing which was causing the blank fields, but I've just re-added it and this is what's actually happening:

1. Data already exists in the table (from a previous session)
2. On navigate to the page with the multiple select combobox, Screen OnVisible creates a collection using ClearCollect.

3. The data in the gallery, including the multiple select combobox, populates correctly, so ThisItem.DefaultSelectItems is working fine (not like I stated earlier that it wasn't)
4. For all fields in the gallery other than the multiple select comboboxes, I patch the data on the back and next buttons.
5. For the multiple select combobox, I patch on OnChange using a ForLoop to get all the selected values in the multiple select combobox, using this code:

ForAll(
    comboBusinessAreasList.SelectedItems,
    Collect(
        colBusinessAreas,
        {
            Value: ThisRecord.Value
        }
    )
);

Patch(BlahTable, ThisItem, {BusinessAreasList:colBusinessAreas.Value}
);

ClearCollect
(colBusinessAreas, Blank());

6. If I navigate away from the page and back to it the values are all fine. So I assume Screen OnVisible is doing it's job and getting the latest values.
7. Now if I update a value in a different control which gets patched on back and next buttons, when I navigate away and then back to this page, the multiple select combobox of the first row loses it's value.

E.g.
This is the current values:

I update FTE of the second row to 3. I patch the values and navigate away. I return and the multiple select combobox for the first row has been cleared:

I'm not sure what could be causing this.

[BCBuizer]

Hi @gabrielaurora ,

Try changing the OnChange property of the Combobox to:

Patch(
    BlahTable, 
    ThisItem, 
    {BusinessAreasList: Self.SelectedItems}
);

[gabrielaurora]

That patched the values (saves me doing the for loop) but I still have the issue. But I think you're on the right track.

I remember when trying a hundred things, I did notice that patching the other controls OnChange had a similar effect with clearing the top row, which is why I put the patch on the back/next button. I didn't patch the combobox as I thought I had to loop. This is my code in the back/next buttons that patches all rows and controls (except the combobox) in the gallery:

ForAll(
      Gallery_1.AllItems
     As memNew,
    Patch(
        BlahTable,
        {
            Col1:memNew.txtCol1.Text
           ,Col2:memNew.ddCol2.Selected.Value
           etc.
        }
    )
);


Navigate('BP Section 4b')

Would you know if I can patch the combobox in the above code? E.g:

ForAll(
      Gallery_1.AllItems
     As memNew,
    Patch(
        BlahTable,
        {
            Col1:memNew.txtCol1.Text
           ,Col2:memNew.ddCol2.Selected.Value
           ,BusinessAreasList:memNew.comboboxBusinessAreasList.??
        }
    )
);


Navigate('BP Section 4b')

I tried Self.SelectedItems was bad syntax.

This BusinessAreasList:memNew.comboBusinessAreasList.SelectedItems patches fine but then still have the issue when I navigate away and then comeback that the first row of the combobox clears.

It's 2 am here so tomorrow I'll take a screen recording of what's happening if that will help make more sense. 

[BCBuizer]

Hi @gabrielaurora ,

Try adding one extra line to the navigations button's OnSelect property to update the collection after patching the data source:

ForAll(
      Gallery_1.AllItems
     As memNew,
    Patch(
        BlahTable,
        {
            Col1:memNew.txtCol1.Text
           ,Col2:memNew.ddCol2.Selected.Value
           etc.
        }
    )
);

ClearCollect(CollectionName, BlahTable);

Navigate('BP Section 4b')

Replace CollectionName with the actual name of the collection.

Ps. I still think you don't actually need to use a collection and connecting the gallery directly to the datasource would fix all your issues. However, the above should fix the issue whilst continuing the use of a collection.

[gabrielaurora]

I tried both of those things and still no joy. I'm changing the screen to use a form now instead of a gallery which will sort my issue but for completeness I've attached a powerpoint with a video of what's happening and what I can't solve.

To clarify the video, when I go to the screen the first time, the data in the multi select comb box is correct. If I update the combox box, click next (patch) and go back, data is fine.
When I update any other field other than the combo box (I call it second field in the video) when I click next (patch) and go back, the data in the combo box for the first row is cleared. Note, the data was patched correctly in the database table it's just displayed incorrectly.