If I'm using Xcode 9 but builiding for iOS 10, the safe area object still shows in the document outline. When I go to Add New Constraints, how do I add a constraint for the top of a view to border right against the bottom of the safe area?
How do I set a constraint of the top of a view against the bottom of the safe area?
You can control-drag from your custom view to the super view. You'll get the menu of constraints you can add between the two, including the safe area. If you use the document outline to find the new constraint just added, you can use the Size Inspector to adjust the relationship to be View.Top = Safe Area.Bottom.
Am I supposed to be able to do it in the Add New Constraints box at the bottom-right hand of the editor (the one that looks like a tie fighter)?
That works too. My main point is to just establish a constraint between the view and the safe area, and then you can use the Size Inspector to adjust the constraint relationship to what you're looking for.