Understanding Swift Programming: Swift 2 (2015)
PART 1: FUNDAMENTALS
PART 2: OBJECT-ORIENTED PROGRAMMING
11. Object-Oriented Programming
12. Classes, Objects, and Inheritance
16. Properties and Class or Type Methods
PART 3: ADDITIONAL TOPICS
17. Functions Revisited: First Class Citizens
18. Closures and Closure Expressions
20. The Flow of Control Revisited: Matching with Patterns
22. Functions Revisited Again: Input Parameters
23. Variations in Closure Expression Syntax
25. Operators Revisited: Overloading and Custom Operators
PART 4: OOP REVISITED
29. Classes Revisited Again: Initializers
30. Type Checking and Type Casting
34. Protocol Oriented Programming
35. Building Mixed Swift and Objective-C Apps
PART 5: APPENDICES
A. What's Different About Swift?