Problem with DatePicker [change] event

Anvil Q&A
1

I have have a function in server module which deals with employees time basically takes two datetime objects as parameters and returns total_working_time as int. When I call this function manually and print its output on form load it works find. However its not working with date picker ‘change’ event.

I have two date picker fields and I want to feed the selected-dates to my function and show their deifference in a text field. Here is the little code I am using

def date_picker_end_time_change(self, **event_args):
    """This method is called when the selected date changes"""
    self.text_box_total_time.text = anvil.server.call('calc_working_time',self.date_picker_start_time.date,self.date_picker_end_time.date)


  def date_picker_start_time_change(self, **event_args):
    """This method is called when the selected date changes"""
      
    self.text_box_total_time.text = anvil.server.call('calc_working_time',self.date_picker_start_time.date,self.date_picker_end_time.date)

Can you please tell me what’s wrong here.

2

what’s the error message you get ?

3

Nothing. The return value of my function never shows up in text field. Actually the same issue is with dropdown box too. The change event doesn’t make a call to server. Here is the code.

 def drop_down_wo_no_change(self, **event_args):
    """This method is called when an item is selected"""
    self.text_box_product.text = anvil.server.call('get_product_in_wo',self.drop_down_wo_no.selected_value)

Here is the server function its calling (The function makes a call to mongodb and returns a particular item in collection).

def get_product_in_wo(wo_id):
  mycol = db['workorders']
  return mycol.find_one({'wo_id':wo_id},{"_id":0,"item":1})['item']

Am I missing something here, or its something to do with Anvil.

4

Step 1 would be to verify that the change-event handler is actually being called. Try inserting a distinctive print function call, one line above the assignment statement. If the handler is being called, you should see the effect of that print in the IDE’s Output window.

3 Likes
5

@p.colbert Brilliant. It just didn’t occur to me whether event is being called or not. Anyway “Change” event was not being called. And I found the culprit. I am using form_checker package as dependency for validation purposes. In case of drop down I mentioned above the validation code is like this

self.validator.require(self.drop_down_wo_no,['change'],
                          lambda wo_no:wo_no.selected_value is not None)

The moment I removed the above code ‘Change’ event started to work. Although its weird, validation library is not supposed to interfere with a component’s basic functionality. Thanks a lot.

6

You’re welcome. :slightly_smiling_face:

When something doesn’t work the way we expect, then usually one of our assumptions is broken. Some of those assumptions can be so “obvious” and subtle, it can be a challenge to recognize which assumptions we’re actually making. But once we do, we can check them, from first to last.

3 Likes