Kotlin State Machines by Étienne Caron

State Machines are a great way to map out Model behavior in your application. They can help you can catch corner cases ahead of time, and are generally a great tool when discussing requirements with product or backend teams.

Despite these advantages, there's often a perception that implementing a state machine is too much work.

In this talk, we'll see how to leverage Kotlin language features to efficiently build State Machines with minimal boilerplate.

https://devfest2019.gdgmontreal.com/speakers/etienne_caron/

Transcript

1. Rise of the State Machines
2. State Machine Head
3. Florence and the State Machine
4. Welcome to the State Machine
5. OFF
6. ON
8. OFF ON switch on switch off
9. OFF ON switch on switch off
10. OFF ON switch on switch off
11. https://github.com/kanawish/android-mvi-sample "
12. https://github.com/kanawish/android-mvi-sample #
13. https://github.com/kanawish/android-mvi-sample # Model Intent View
16. IDLE PROCESS ERROR refresh check task success failed
17. sealed class SyncState { object IDLE : SyncState() { override fun toString(): String = "IDLE" } data class PROCESS(val type: Type) : SyncState() { enum class Type { REFRESH, CHECK } } data class ERROR(val throwable: Throwable) : SyncState() } IDLE PROCESS ERROR refresh check task success failed
18. sealed class SyncState { object IDLE : SyncState() { override fun toString(): String = "IDLE" } data class PROCESS(val type: Type) : SyncState() { enum class Type { REFRESH, CHECK } } data class ERROR(val throwable: Throwable) : SyncState() } IDLE PROCESS ERROR refresh check task success failed
19. Model ModelState store
20. Model ModelState store «data class» TasksModelState tasks: List<Task>
21. Model ModelState store «data class» TasksModelState tasks: List<Task> Task id: String lastUpdate: Long title: String description: String completed: Boolean tasks
22. «data class» TasksModelState tasks: List<Task> Model ModelState store Task id: String lastUpdate: Long title: String description: String completed: Boolean tasks «sealed class» SyncState Idle() Process(type) Error(details) syncState syncState: SyncState
23. «data class» TasksModelState tasks: List<Task> Model ModelState store Task id: String lastUpdate: Long title: String description: String completed: Boolean tasks «sealed class» SyncState Idle() Process(type) Error(details) syncState syncState: SyncState
24. «data class» TasksModelState tasks: List<Task> Model ModelState store Task id: String lastUpdate: Long title: String description: String completed: Boolean tasks «sealed class» SyncState Idle() Process(type) Error(details) syncState syncState: SyncState IDLE PROCESS ERROR refresh check task success failed
25. Live demo
26. Live demo
29. CLOSED EDITING task error? SAVING task DELETING taskId addTask() editTask() cancel() edit() save() error(msg) delete() error(msg) deleted() saved()
30. Live demo
31. Live demo