Using the NSLayoutConstraint class, it is possible to create a constraint that is based on a view's baseline (NSLayoutAttributeBaseline). However, I haven't seen any documentation that describes how a UIView actually provides a baseline value to the auto layout system.
If I wanted to create a custom UIView subclass that defines a baseline, how would I do it? NSView defines a baselineOffsetFromBottom method that I assume is involved somehow on OS X, but how does this work in iOS?
From the UIView docs:
viewForBaselineLayoutReturns a view used to satisfy baseline constraints.
- (UIView *)viewForBaselineLayoutReturn Value
The view the constraint system should use to satisfy baseline constraints