Find what default events an object has

Anvil Q&A
1

What I’m trying to do:
Create a method that adds events to an object based on the events that object has by default.

What I’ve tried and what’s not working:

I have tried using the augment class from anvil_extras, but if the object already has the event being set, it will be raised twice.

I could easily solve my issue by checking what obj has what event and putting if statements, but I’d like to check if the event is a default event programmatically.

Code Sample:

def add_event(obj):
    augment.set_event_handler(obj,'click',self.alter_color)  #If the Obj is a button, click will be raised twice.
2

I’m not sure I totally follow the question. But you might find get_event_handlers a useful piece of api. See the component api docs

1 Like
3

Thank you for pointing me to that document.

Here is a clone to illustrate my issue:

You’ll see that clicking the label will yield a single “Clicked” print statement where the button will print two “Clicked” statements.

When printing out the event handlers using the get_event_handlers method, they both only have a single event handler.

What I was looking for was a method that is more akin to get_default_events. This would allow me to detect that the button object already has a default “click” event without knowing its type before hand. I could than use the objects add_event_handler instead of using augment, to avoid the double click that occurs.

4

Ah that makes sense, thanks for providing the clone.

The augment module isn’t designed to augment existing Anvil events, such as augmenting a Button with a "click" event. That explains why it isn’t functioning as anticipated. I’ve implemented a fix, and it should work as expected soon.

There isn’t a method to determine which events are available for a specific component.

On a side note,
I presume you’re attempting more than simply making elements clickable? If your sole aim is to create a clickable object, you can wrap it in a Link Component and assign the click event handler to the Link component.

There may be a more suitable approach to addressing the issue you’re encountering, but it’s difficult to make a better suggestion without knowing the initial problem that prompted the question.

1 Like
5

I appreciate it!

For more context, I am working on a creating tool that will allow you to add a container and any type of object to it and give that object a few properties:

  1. Alternate color on hover
  2. select and alternate color on click
  3. Be able to drag-select multiple items

Then you would be able to pull all the selected items similar to the multi-drop-down object.

It’s hard to capture the drag-select feature via a gif but here are all three properties on display:

file

This is how I currently avoid the issue.

  def add_item(self,key,value):
    self.selected_map[key] = value
    key.set_event_handler('click',self.select_item)
    augment.add_event_handler(key,'hover',self.alter_color)
    augment.add_event_handler(key,'mouseleave',self.final_color)
    augment.add_event_handler(key,'hover',self.select_item_drag)

I have a few other ideas in mind and want to do a show-n-tell post, but I’d like to make it robust before that. I thought, if there was an easy way to dynamically determine which objects-event pairs would fire twice, I could avoid some headaches.

EDIT: Updated the context statement above with the italic containter portion.

6

We’ve fixed that bug now on the anvil-extras development dependency.

Looking forward to the show and tell!

1 Like