Inter-pages callback in MultiPage App

Dash Python
1

Hello again!))

I have a multipage app.

  1. Page http://localhost:8050/events/ where there is Ag Grid table
  2. Page http://localhost:8050/event/<event_id> where there is a Button for closing event.

I want to send an update transaction to AgGrid table when clicking “Close event” button.

But it turned out that callbacks can interact only with elements on the same page.
I tried to use proxy-Store placed in the main layout but it didn’t work out.

@dashapp.callback(
    Output('events-table', 'rowTransaction'),
    Input('globstore', 'data'),
    prevent_initial_call=True,
)
def update_table(transaction):
    return {'update': transaction}

This callback can’t be triggered regardless of it is placed in the events.py or main.py.
However the following callback on the event/<event_id> page works

@callback(
    Output('globstore', 'data'),
    Input('is-incident-btn', 'n_clicks'),
    State('event-id', 'data'),
    prevent_initial_call=True
)
def write_transaction(clicks, event_id):
    if not clicks:
        raise PreventUpdate
    transaction = [{'_id': event_id, 'is_incident': True}]
    return transaction

Is there any solution?

2

Hello @yukian72,

Can you provide a full example code to demonstrate what you’ve tried?

3
main.py 
def init_app(server: Flask, path: str):

    dashapp = Dash(__name__, server=server, external_stylesheets=dmc.styles.ALL,
                   url_base_pathname=path,
                   use_pages=True,
                   suppress_callback_exceptions=True)

    store = dcc.Store(id='globstore', data=1)

    layout = dmc.AppShell(
        children=[
            
            dmc.AppShellHeader(),

            dmc.AppShellNavbar(
                children=[
                    dmc.NavLink(
                        label="События",
                        leftSection=DashIconify(icon='material-symbols:e911-emergency', height=24),
                        href='/events/',
                    )
                ],
                p='md'
            ),

            dmc.AppShellMain([store, page_container]),

        ],
    )


    dashapp.layout = dmc.MantineProvider(layout, forceColorScheme='dark')


    return dashapp.server
pages/events.py 
dash.register_page(__name__)

...

table = dag.AgGrid(
    id="events-table",
    className='ag-theme-quartz-dark',
    dashGridOptions={'pagination': True,
                     'paginationPageSize': 30,
                     'domLayout': 'autoHeight',
                     'rowSelection': 'multiple',
                     'suppressRowClickSelection': True},
    getRowId='params.data._id',
    rowClassRules=rowClassRules,
    style={'height': None},
    eventListeners={'rowDataUpdated': ['refreshCells(params, setGridProps)']}
)

...

@callback(
    Output('events-table', 'rowTransaction', allow_duplicate=True),
    Input('globstore', 'data'),
    prevent_initial_call=True,
)
def update_table(transaction):
    return {'update': [transaction]}

layout = html.Div(
    children=[
        dmc.Container(table, fluid=True, style={"marginTop": 7}),
    ]
)

Column ‘description’ is defined as follows

{
    'field': 'description',
    'headerName': 'Description',
    'flex': 1,
    'cellRenderer': 'eventLink',
    'wrapText': True,
}

The links in this column have format ‘https://localhost/event/<event_id>’

pages/event.py 
dash.register_page(__name__, path_template='/event/<event_id>')

...

@callback(
    Output('globstore', 'data'),
    Input('close-event-btn', 'n_clicks'),
    State('event-id', 'data'),
    State('globstore', 'data'),
    prevent_initial_call=True
)
def write_transaction(clicks, event_id, data):
    if not clicks:
        raise PreventUpdate
    transaction = {'_id': event_id, 'is_closed': True}
    return transaction

My notes:

  1. Callback write_transaction is working. It writes transaction details in globstore
  2. Callback update_table doesn’t trigger. ONE TIME during many runs is was triggered. I don’t know how)) But It didn’t happen anymore. And I think that time callback write_transaction wasn’t triggered.
  3. I’ve found Passing data between pages via a dcc.Store · Issue #94 · plotly/dash-labs · GitHub
  4. I use Flask in my project so that’s the reason why my dashapp is defined inside INIT_APP function.
4

Thanks for the code, there are still some blanks, check out here to help with troubleshooting your issue as there is too much for me to try to figure out.

5

I prepared a toy project for experiments GitHub - Y0shiT0shi/dash-inter-pages-callbacks

I decided to use DashExtensions Pages to share one AgGrid between different app pages. And in general it even partially works. Steps to check:

  1. Open app
  2. Go to the second page and have a look at the table
  3. Click button → new row added
  4. Go to the first page and click the button there
  5. Go to the second page again → new row from clicking the button on the first page added as well

But.. if you do that:

  1. Open app
  2. Open the second page in a new browser tab
  3. Click button → new row added
  4. Switch to the first browser tab with the first page opened → click the button → go to the second page in the first browser tab → ONLY row from this step has been added

It looks like we have two different tables despite the fact that we have only one AgGrid component.
I tried to play with persistence property of AgGrid but had no success.
I want to open events in separate tabs so this behavior is a problem.

6

Yes, the data is not shared across tabs, that would take using something linking the two together. You will need something like websockets, or a db to store the info against a user.

If you want to use that, then you need to do a little more work too.

Here is an example of using a global variable:

This is not the recommended path, but just demoing how you’d perform it.