First, let's start with some helpful resources:

iOS Design

• Apple's Human Interface Guidelines
• WWDC 2015 Videos
  • Designing For Future Hardware (This is more about prototyping and incredibly informative)
• WWDC 2014 Videos
  • Creating Custom iOS User Interfaces
  • Designing Intuitive User Experiences
  • Making a Great First Impression With Strong Onboarding Design
  • Prototyping: Fake It Till You Make It
• WWDC 2013 Videos
  • Customizing Your App’s Appearance for iOS 7 (Still valid for iOS 8)
  • Building User Interfaces for iOS 7 (Still valid for iOS 8)

Development Introductions

• Apple's Intro Documentation
• Apple's iBooks

Development In Depth

• Maybe Haskell
• NSHipster
• Thoughtbot's blog

If you're already familiar with Objective-C, an effective strategy can be to simply begin by writing Objective-C in Swift. That is to say, don't worry about any of the new or different features, just interact with Apple's frameworks like you used to as much as possible and keep working. Later, as you become more comfortable with the language and learn about the more in-depth features, go back and refactor your code to make effective use of all the Applicatives and Monads you like. Just because Swift has fancy features in the language doesn't mean you need to use them on day one.