Why I'm not able to redraw a line?

[Nowhk]

This is the situation I have:

redraw.png (24.01 KiB) Viewed 8382 times

I'd like to redraw the line (i.e. its height) every time I tweak the knob.

I can see the value change using "watch", but the line is not redraft. Where am I wrong?
Hope you can help me.

Thanks for your time, as usual!

[tulamide]

All inputs you name are automatically converted to an instance variable. So your input "height" is also available as @height. But you also declare another variable as @height. Rename one of them.

[Nowhk]

All inputs you name are automatically converted to an instance variable. So your input "height" is also available as @height. But you also declare another variable as @height. Rename one of them.

Uhm, nothing change

Immagine.png (23.35 KiB) Viewed 8379 times

moving knob, I can't see any redraft....

[Nowhk]

Oh no wait, it works! Just I can't see move it in the preview in the top! Thanks