I feel guilty for asking question I can not properly name because I can not name the pattern used in the code.
There is a code on github I'm trying to understand and failing to do so. https://github.com/kivy-garden/speedmeter/blob/master/kivy_garden/speedmeter/init.py
Pattern I don't understand is in lines 128,129 and 181, 182 and many other places.
Big picture is. There a class
class MyClassName(Widget):
there are methods e.g.
def _draw_this_and_that(self):
self._someName.clear()
add = self._someName.add
add(Color(rgba=get_color_from_hex(color)))
This "_someName" found in whole code only in those 2 places as my code sample.
I understand that
add = self._someName.add
creates function "add" but why that is needed? why not calling
self._someName.add
instead?
I guess that
self._someName.clear()
does erase whatever was added to "_someName", right?
I completely do not understand how
add(Color(rgba=get_color_from_hex(color)))
does it job (but it does) and then whatever is drawn will be with that color.
Do I guess it right that if I need to change color (if some condition met) then I could just add different color?
add(Color(rgba=get_color_from_hex(different_color)))
and don't stress that adding will cause memory leak because
self._someName.clear()
will take care of it?
I never seen such pattern. I'd be very happy if someone could explain how it works and why. Thank you in advance!
The _somenameIG are canvas instruction groups that are created in the __init__() method:
add = self.canvas.add
for instructionGroupName in _ig:
ig = InstructionGroup()
setattr(self, '_%sIG' % instructionGroupName, ig)
add(ig)
So, the self._someName.clear() is clearing a canvas instruction group, and the add() method adds instructions to the group.