This is clearly why they bought Teehan and Lax
Well done, Facebook. This makes Apple look kinda bad, they should have been the ones providing these to the design community IMHO.
Sometimes I feel like the iOS design team at Facebook is a sort of walled kindergarten filled w/ awesome nice people.
I don't think it's that dissimilar to Google though.
As someone who does nothing but complain, I want to take this opportunity to say "class act" and "well done" to the folks who made this.
You're a good guy, Todd.
Bravo FB team, this is great work. As a side note I'd love to see something this detailed for Material design.