Polymorphism with Protocols

Good API design is essential for writing code that scales. In this talk, we look at some characteristics of good design and how to refactor code using the protocol features in Swift.

Source code available at https://github.com/matthewcheok/polymorphism-with-protocols

Video at https://youtu.be/2fO-B4qL8ZA

Transcript

1. Polymorphism with Protocols
2. Good API Design is... ! "
5. Naive Approach class Node { var value: Double? var operation: String? var leftChild: Node? var rightChild: Node? func evaluate() -> Double }
6. Values class Node { var value: Double? var operation: String? var leftChild: Node? var rightChild: Node? func evaluate() -> Double }
7. Operations class Node { var value: Double? var operation: String? var leftChild: Node? var rightChild: Node? func evaluate() -> Double }
8. Is this reasonable? !
9. Optionals? Everywhere class Node { var value: Double? var operation: String? var leftChild: Node? var rightChild: Node? func evaluate() -> Double }
10. Which can be nil? class Node { var value: Double? var operation: String? var leftChild: Node? var rightChild: Node? func evaluate() -> Double }
11. Structs or Classes? class Node { var value: Double? ... } struct Node { var value: Double? ... }
12. What happens if we do this? node.leftChild = nil
13. What we did • Naive class implementation • Introducing abstract classes • Moving into protocols (value types) • Implementing a third-party protocol (rendering) (protocol extensions)
14. Additional Readings Inheritance, Polymorphism, & Testing Misko Hevery Everyone is an API designer John Sundell Playground Quicklook for Binary Trees Swift Talk
15. Thank You @matthewcheok