State Management & Unidirectional Data Flow in Swift

Transcript

1. @nikolasburk State Management & Unidirectional Data Flow State Management & Unidirectional Data Flow “Where is truth in your application?” Andy Matuschak, WWDC 2014
2. Nikolas Burk @nikolasburk • Developer at Graphcool • Experienced with iOS • Passionate about programming paradigms and architecture
3. 1. State Management 2. Unidirectional Data Flow & ReSwift @nikolasburk State Management & Unidirectional Data Flow Goals
4. State Management …and why it matters to you
5. @nikolasburk State Management & Unidirectional Data Flow
6. @nikolasburk State Management & Unidirectional Data Flow An Application is more than the Happy Path “In the context of software or information modeling, a happy path is a default scenario featuring no exceptional or error conditions.” Wikipedia
7. @nikolasburk State Management & Unidirectional Data Flow Decision process for Slack Notifications
8. The application state represents the information that is kept in memory of a running application and is the basis for the generation of a user interface. Application State? @nikolasburk State Management & Unidirectional Data Flow
9. The application state represents the information that is kept in memory of a running application and is the basis for the generation of a user interface. Application State? @nikolasburk State Management & Unidirectional Data Flow
10. The application state represents the information that is kept in memory of a running application and is the basis for the generation of a user interface. Application State? @nikolasburk State Management & Unidirectional Data Flow
11. @nikolasburk State Management & Unidirectional Data Flow The main responsibility of an app is to transform an application state into a user interface. (AppState) -> UI
12. Example: Conference Planner App @nikolasburk State Management & Unidirectional Data Flow struct Conference { let name: String let city: String let year: String var attending: Bool }
13. Application State? @nikolasburk State Management & Unidirectional Data Flow conferences = [ Conference( name: "AppDevcon", city: "Amsterdam", year: "2017", attending: true ), Conference( name: "UIKonf", city: "Berlin", year: "2017", attending: false ), Conference( name: "WWDC", city: "San Jose", year: "2017", attending: true ) ]
14. Application State? @nikolasburk State Management & Unidirectional Data Flow conferences = [ Conference( name: "AppDevcon", city: "Amsterdam", year: "2017", attending: true ), Conference( name: "UIKonf", city: "Berlin", year: "2017", attending: false ), Conference( name: "WWDC", city: "San Jose", year: "2017", attending: true ) ] selectedIndex = 0
15. Application State? @nikolasburk State Management & Unidirectional Data Flow conferences = [ Conference( name: "AppDevcon", city: "Amsterdam", year: "2017", attending: true ), Conference( name: "UIKonf", city: "Berlin", year: "2017", attending: false ), Conference( name: "WWDC", city: "San Jose", year: "2017", attending: true ) ] selectedIndex = nil
16. @nikolasburk State Management & Unidirectional Data Flow 1. Where should the state live? 2. Who is allowed to change the state? 3. How does the state get changed? 3 Golden Questions of State Management An architectural pattern should be able to answer these questions!
17. @nikolasburk State Management & Unidirectional Data Flow Model View Controller
18. @nikolasburk State Management & Unidirectional Data Flow Where should state live? 1
19. @nikolasburk State Management & Unidirectional Data Flow Who is allowed to change the state? 2
20. @nikolasburk State Management & Unidirectional Data Flow How does the state get changed? KVO & Property Observers Delegates Callbacks NSNotificationCenter Target-Action 3
21. @nikolasburk State Management & Unidirectional Data Flow UIViewController What’s wrong with MVC? Persistence Networking Navigation Domain Logic User Interface Concurrency
22. @nikolasburk State Management & Unidirectional Data Flow State Management is hard and MVC is not a solution, thanks Apple
23. Unidirectional Data Flow … and controlling your application state with ReSwift
24. @nikolasburk State Management & Unidirectional Data Flow • 3 Principles • Single source of truth • State is read-only • Changes with pure functions http://redux.js.org/docs/introduction/ThreePrinciples.html
25. @nikolasburk State Management & Unidirectional Data Flow Main Concepts Store: … manages the application state … informs subscribers about changes Actions: … describe an intent to change the state Reducer: … pure functions that generate a new application state based on actions
26. Example Flow @nikolasburk State Management & Unidirectional Data Flow
27. Application State (Old) AppDevcon UIKonf WWDC Reducer add Swift Summit to list and return new application state Action “Swift Summit” “San Francisco” “2017” Application State (New) AppDevcon UIKonf WWDC Swift Summit
28. @nikolasburk State Management & Unidirectional Data Flow Helpful Resources • Unidirectional Data Flow in Swift: An Alternative to Massive View Controllers (Video) (https://realm.io/news/benji-encz- unidirectional-data-flow-swift/) • Real World Flux Architecture on iOS (http://blog.benjamin- encz.de/post/real-world-flux-ios/) • Redux Documentation (http://redux.js.org/) • Advanced iOS Application Architecture and Patterns, Andy Matuschak WWDC 2014 (Video) (http://asciiwwdc.com/2014/ sessions/229)
29. DEMO Conference Planner App
31. Thank you! @nikolasburk