Using Xcode 6.0, you can now specify proportional width or height in Interface Builder.
Steps for percentage height from superview:
While both the child view and its superview are selected, add an "equal height" constraint (or "equal width" if you wish to have a proportional width).
Then change the "multiplier" of the constraint you just added to the proportion you need. For example, for 50%, change it to 2.
If you like to specify the inner view as percentage of the superview, you can reverse the items in the constraint:
Now you can use a multiplier of 0.5 (or any other proportion you need):
In your specific case, you can define an "equal height" constraint between the 2 child views, and change the multiplier to 1.5 (the bottom being 1.5 the size of the top) or 0.6667 if the items are reversed.
See also How to make constant auto-resize in Storyboard?
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…