constraints - Xcode Auto Layout: Can't resize window -

what want achieve:

custom view 1    aligned @ top    fixed height = 20px    width = window width  horizontal split view    below custom view    width = window width    height = large possible  custom view 2    aligned @ bottom    fixed height = 20px    width = window width 

it's simple layout: header , footer @ top , bottom of window, , split view in between content left , right should resize window. however, apple designed auto layout manager poorly, can't seem work. (i've fumbled around 3 hours now!)

the problem is: give custom views fixed height, window height locked, can't resize vertically more. i'm trying following constraints:

custom view 1     constraints     height = 20px  custom view 2     height = 20px  constraints     leading horiz space custom view 1 superview = 0     leading horiz space custom view 2 superview = 0     leading horiz space split view superview = 0     trailing horiz space custom view 1 superview = 0     trailing horiz space custom view 2 superview = 0     trailing horiz space split view superview = 0      top vert space between custom view 1 , superview = 0     vert space between custom view 1 , split view = 0     vert space between custom view 2 , split view = 0     bottom vert space between custom view 2 , superview = 0     top vert space between custom view 2 , superview = 344px (!) 

the last line added xcode, , can't delete it. of course, responsible fixed vertical layout. how can rid of it???

ok, figured out.

i had leave ib's redundant constraint in, give priority of 1. ib had given priority of 1000, overriding constraint.