handle_delete-method ist never invoked in an ui.View

[kathodenfreak]

Hello community,

I‘am trying to create an application that allows me to retrieve a set of photos from an sqlite3-database and should give me the possibility to delete an entry via the handle_delete()-Method. The photos are retrieved and shown in the table_view, the delete_button is shown in the table_view but unfortunately the handle_delete()-method ist never invoked.

Any ideas about that?

Thanks in advance

class FotoBrowser(ui.View):
def init(self):
super().init()
self.frame = (0, 0, 600, 400)
self.background_color = "white"

    # Der Bereich links, in dem die Dateinamen ausgegeben werden
    self.table_view = ui.TableView(frame=(0, 0, 200, 400))
    self.add_subview(self.table_view)

    # Der Bereich rechts, in dem die Fotos ausgegeben werden
    self.iv = ui.ImageView(frame=(210, 0, 380, 400))
    self.iv.content_mode = ui.CONTENT_SCALE_ASPECT_FIT
    self.iv.background_color = "white"
    self.iv.current_id = None
    self.add_subview(self.iv)

    # DataSource einmalig erstellen
    self.ds = ui.ListDataSource([])
    self.ds.delete_enabled = True
    self.ds.action = self.did_select
    self.ds.delete_action = self.handle_delete  # Einmalig setzen
    self.table_view.data_source = self.ds
    self.table_view.delegate = self.ds

    # Initial die Liste laden
    self.reload_list()

# ------------------- Liste aktualisieren -------------------
def reload_list(self):
    self.bilder = lade_bilder_aus_db()
    self.ds.items = [f"ID {id_}: {name}" for (id_, name) in self.bilder]
    self.table_view.reload()  # Tabelle neu laden

# ------------------- Auswahl -------------------
def did_select(self, sender):
    print("did_select")
    row = sender.selected_row
    if row < 0:
        return
    foto_id, _ = self.bilder[row]
    blob = lade_blob_aus_db(foto_id)
    if blob:
        self.iv.image = blob_to_ui_image(blob)
        self.iv.current_id = foto_id
    else:
        self.iv.image = None
        self.iv.current_id = None

# ------------------- Löschen -------------------
def handle_delete(self, ds_inner, row): # NEVER CALLED! WHY?
    print("handle_delete")
    foto_id, _ = self.bilder[row]
    # Rechte Seite leeren, falls gerade angezeigt
    if self.iv.current_id == foto_id:
        self.iv.image = None
        self.iv.current_id = None
    # Datensatz löschen
    loesche_datensatz(foto_id)
    # Liste neu laden
    self.reload_list()

------------------- Start -------------------

if name == "main":
browser = FotoBrowser()
#print(ui.ListDataSource.str)
browser.present("sheet")

[cvpe]

Pythonista doc for ListDataSource describes attribute edit_action called when row is deleted, never seen "your" delete_action.

[kathodenfreak]

Yes I know. I have a delete button in my table_view when I swipe left. Then the entry in ListDataSource is deleted so it should invoke the handle_delete method what never happens. You mean I should set self.edit_action to handle_delete()? I can give it a try. Thanks for your advise.

[cvpe]

Yes, there is no delete_action attribute, are you sure you did see that somewhere?
Doc says to write

self.ds.edit_action = self.handle_delete

ListDataSource.edit_action#
Called when rows are deleted or rearranged. The sender argument of the action will be the ListDataSource object. The items attribute is already updated when the action is called.

[RichardPotthoff]

I have asked Grok to comment on this issue. Here is the response:

Comment on GitHub Discussion #92

The core issue here is a mismatch between the code and Pythonista's ui.ListDataSource API: there's no delete_action attribute (that's why handle_delete never fires). Instead, use edit_action, which handles both deletions (via swipe-to-delete) and row rearrangements. This is confirmed in the official docs.

Additionally:

• The callback signature for edit_action is def handle_delete(self, datasource) (where datasource is the ListDataSource instance). It doesn't pass a row index directly.
• When edit_action runs, datasource.items is already updated (the deleted item is gone). To identify the deleted row for DB cleanup:
  • Track the pre-deletion state (e.g., store old_items = self.ds.items[:] before enabling edits, but since deletes happen interactively, a better approach is to parse the removed item from a comparison of old vs. new items lists.
  • Since your items are formatted as "ID {id_}: {name}", you can diff the lists to extract the missing ID.

Here's the fixed code snippet for your FotoBrowser class (I've also corrected init to __init__ for proper inheritance, assuming that was a copy-paste error). I added a helper to detect the deleted ID via list diffing—simple and reliable for single deletes.

import ui

class FotoBrowser(ui.View):
    def __init__(self):
        super().__init__()
        self.frame = (0, 0, 600, 400)
        self.background_color = "white"

        # Left area for filenames
        self.table_view = ui.TableView(frame=(0, 0, 200, 400))
        self.add_subview(self.table_view)

        # Right area for photos
        self.iv = ui.ImageView(frame=(210, 0, 380, 400))
        self.iv.content_mode = ui.CONTENT_SCALE_ASPECT_FIT
        self.iv.background_color = "white"
        self.iv.current_id = None
        self.add_subview(self.iv)

        # DataSource setup
        self.bilder = []  # Store full data here
        self.ds = ui.ListDataSource([])
        self.ds.delete_enabled = True
        self.ds.action = self.did_select
        self.ds.edit_action = self.handle_delete  # Fixed: use edit_action
        self.table_view.data_source = self.ds
        self.table_view.delegate = self.ds

        # Initial load
        self.reload_list()

    def reload_list(self):
        self.bilder = lade_bilder_aus_db()  # Assuming this returns list of (id_, name) tuples
        self.ds.items = [f"ID {id_}: {name}" for (id_, name) in self.bilder]
        self.table_view.reload()

    def did_select(self, sender):
        print("did_select")
        row = sender.selected_row
        if row < 0:
            return
        foto_id, _ = self.bilder[row]
        blob = lade_blob_aus_db(foto_id)
        if blob:
            self.iv.image = blob_to_ui_image(blob)
            self.iv.current_id = foto_id
        else:
            self.iv.image = None
            self.iv.current_id = None

    def handle_delete(self, datasource):  # Fixed: only 'datasource' arg
        print("handle_delete")
        # Detect deleted item by comparing old vs. new items
        old_items = [f"ID {id_}: {name}" for (id_, name) in self.bilder]  # Reconstruct expected old list
        new_items = datasource.items
        # Find the missing item (assumes single delete; for multi, adapt accordingly)
        deleted_item = next((item for item in old_items if item not in new_items), None)
        if deleted_item:
            # Parse ID from string (e.g., "ID 123: filename.jpg" -> 123)
            foto_id = int(deleted_item.split(':')[0].split()[-1])
            # Clear image if showing deleted foto
            if self.iv.current_id == foto_id:
                self.iv.image = None
                self.iv.current_id = None
            # Delete from DB
            loesche_datensatz(foto_id)
        # Reload to sync everything
        self.reload_list()

# Start
if __name__ == "__main__":
    browser = FotoBrowser()
    browser.present("sheet")

Quick Explanation

• Why this works: edit_action triggers on swipe-delete. The diff logic identifies the removed string, parses the ID, and cleans up the DB/image view.
• Edge cases: Handles single deletes fine (standard swipe behavior). For batch edits/rearranges, you'd need more robust diffing (e.g., using difflib), but that's rare here.
• Test tip: Run in Pythonista; swipe left on a row to trigger.

This should resolve it—drop this as a reply on the thread! If multi-row edits are needed, let me know for tweaks.