ios - Why do autolayout constraints in Xcode cause my subview to disappear off screen? -

i'm trying figure out how use autolayout, , there seems lack of info on internet. placed view within view controller 3 buttons inside it. before place constraints, buttons show on preview. however, make constraints, whole sub view stops showing in preview. made constraint center vertically, , 1 place 25 pixels left edge. should know place it, still nothing shows up.

any ideas on why constraints cause buttons not show up?

with autolayouts constraints should clear possible. can try adding size constraints fix(right, top or bottom) constraints if necessary.