How do I use auto-layout to make a child view fill its parent, or at least anchor all its edges to the parent view\'s edges?
I am using all four vertical and horizon
I would just set all "Spacing to nearest neighbor" to 0, and align horizontal and vertical center. That should do the trick.
Pin the top space to superview, bottom space to superview, leading space to superview and trailing space to superview.

Then set edit the constraints like so:
Superview.Top >= View.Top and Superview.Bottom >= View.Bottom