None as target_object for bindings

[rolfn]

A suggestion:
It would be good if it were possible to specify None for the first parameter of .bind_enabled_from, .bind_visibility, etc. (target_object). In this case, only backward would be functional. It would then be easy to implement something like the following:

ui.button('OK') \
.bind_enabled_from(None, backward=lambda _: my_very_complicated_function())

or

ui.button('OK') \
.bind_enabled_from(None, backward=lambda _: input_1.value and input_2.value)

Forgive me if I've overlooked something simple.

[falkoschindler]

What would be the expected outcome?
It seems like you want the button to be automatically enabled based on two sources. But NiceGUI wouldn't know when to call the function. It would need to call it repeatedly (like for "active links"), which would be equivalent to

b = ui.button('OK')
ui.timer(0.1, lambda: b.set_enabled(input_1.value and input_2.value))

From my point of view, a timer feels more readable and explicit than using a "bind" function with None target.

[rolfn]

My intention was a simple syntax for dependencies from more than one source. Sometimes I use this working workaround:

bind_dummy = { 'visible':False, 'enabled':False }
...
ui.button('OK') \
.bind_enabled_from(bind_dummy, backward=lambda _: input_1.value and input_2.value)

I thought that using None might emulate this. Just an idea...