Multiplatform Persistence

A lot of client code is already multiplatform - the tools underneath client backends like SQLite, protobufs, and HTTP are themselves platform agnostic. Codebases for Android and iOS already look similar on top of these tools until exposed to platform specific interfaces. Realistically how much could be shared across multiple platforms without affecting any codebase significantly?

This talk will go over SQLDelight 1.0 - a recent release which has enabled multiplatform SQLite development using Kotlin Native, as well as how to architect your app’s data layer to be shared across platforms. It will focus on how SQLDelight can be best used from both Android and iOS while feeling natural to Kotlin and Swift users alike, and go over features introduced in the release that affect all platforms. Finally we will explore the future of multiplatform including other components of your app which are good or bad candidates for making platform agnostic and what future releases of SQLDelight will include.

Transcript

1. Multiplatform
 Persistence
3. message Customer { required int32 id = 1; required string name = 2; required string photoUrl = 3; } message Payment { required Money amount = 1; required int32 sender = 2; required int32 recipient = 3; } protos
4. message Customer { required int32 id = 1; required string name = 2; required string photoUrl = 3; } message Payment { required Money amount = 1; required int32 sender = 2; required int32 recipient = 3; } protos
5. public interface AppService { @POST("/2.0/cash/sync-entities") // Observable<SyncEntitiesResponse> syncEntities( @Body SyncEntitiesRequest request); }
6. public interface AppService { @POST("/2.0/cash/sync-entities") // Observable<SyncEntitiesResponse> syncEntities( @Body SyncEntitiesRequest request); } protos api
7. CREATE TABLE contact ( lookup_key TEXT PRIMARY KEY, display_name TEXT ); CREATE TABLE alias ( hashed_alias TEXT NOT NULL PRIMARY KEY, email TEXT, sms TEXT, customer_id TEXT REFERENCES customer ); CREATE TABLE customer ( customer_id TEXT PRIMARY KEY, photo_url TEXT, customer_display_name TEXT );
8. CREATE TABLE contact ( lookup_key TEXT PRIMARY KEY, display_name TEXT ); CREATE TABLE alias ( hashed_alias TEXT NOT NULL PRIMARY KEY, email TEXT, sms TEXT, customer_id TEXT REFERENCES customer ); CREATE TABLE customer ( customer_id TEXT PRIMARY KEY, photo_url TEXT, customer_display_name TEXT ); db protos api
9. backend db protos api
10. backend presenters db protos api
11. backend presenters viewmodel + viewevent db protos api
12. backend presenters viewmodel + viewevent app db protos api
13. db protos api presenters viewmodel + viewevent app backend val presenter = ActivityPresenter()
14. val presenter = ActivityPresenter() db protos api presenters viewmodel + viewevent app backend entitySyncer.triggerSync( foreground = false, force = false ).subscribe() appService.syncEntities(request) @POST("/2.0/cash/sync-entities") // Observable<SyncEntitiesResponse> syncEntities( @Body SyncEntitiesRequest request); paymentQueries.insertPayment( payment.token!!, payment.sender_id, payment.recipient_id, payment.amount ) insertPayment: INSERT OR REPLACE INTO payment (token, sender_id, recipient_id, amount) VALUES (?, ?, ?, ?); fun renderedPayment( paymentToken: String ): Observable<RenderedPayment> entityManager .renderedPayment(token) .map(this::createViewModel) .subscribe(view) presenter.viewModel() .observeOn(AndroidSchedulers.mainThread()) .subscribe(this::renderViewModel)
15. db protos api presenters viewmodel + viewevent app backend
16. interface InstrumentManager { @CheckResult fun withToken( token: String ): Observable<Instrument> } backend
17. internal class RealInstrumentManager @Inject constructor( private val appService: AppService, private val queryWrapper: QueryWrapper, @Io private val ioScheduler: Scheduler ) : InstrumentManager backend
18. internal class RealInstrumentManager @Inject constructor( private val appService: AppService, private val queryWrapper: QueryWrapper, @Io private val ioScheduler: Scheduler ) : InstrumentManager backend
19. internal class RealInstrumentManager @Inject constructor( private val appService: AppService, private val queryWrapper: QueryWrapper, @Io private val ioScheduler: Scheduler ) : InstrumentManager backend
20. class RealInstrumentManagerTest { @get:Rule private val temporaryDatabase = TemporaryDatabase() @Before fun before() { val appService = FakeAppService() val queryWrapper = temporaryDatabase.queryWrapper instrumentManager = RealInstrumentManager( appService = appService, queryWrapper = queryWrapper, ioScheduler = Schedulers.trampoline() ) } } backend
21. db protos api presenters viewmodel + viewevent app backend
22. db protos api presenters viewmodel + viewevent app backend
27. db backend api presenters viewmodel + viewevent app protos
28. protos Wire protobufs
29. db backend presenters viewmodel + viewevent app protos api
30. api Retrofit Http protos RxJava
31. backend presenters viewmodel + viewevent app protos api db
32. db SQLite SqlDelight SqlBrite
33. presenters viewmodel + viewevent app protos api backend db
34. backend dagger db api RxJava
35. viewmodel + viewevent app protos api db presenters backend
36. presenters backend viewmodels analytics RxJava
37. viewmodel + viewevent app api db protos presenters backend
38. viewmodel + viewevent app api db protos presenters backend
39. viewmodel + viewevent app api db protos presenters backend
40. protos Wire protobufs
41. protos Wire protobufs parcelable
42. viewmodel + viewevent app api presenters db protos backend
43. viewmodel + viewevent app api presenters protos backend db
44. db SQLite SqlDelight SqlBrite
45. db SqlDelight SqlBrite
46. db SqlBrite SqlDelight
47. db SqlBrite SqlDelight
48. db SqlBrite SqlDelight
49. SqlDelight 1.0
50. SqlDelight 1.0 (alpha)
51. Player.sq: CREATE TABLE player ( id INTEGER NOT NULL PRIMARY KEY, name TEXT NOT NULL, country TEXT NOT NULL ); build/Player.kt: interface Player { val id: Long val name: String val country: String data class Impl( override val id: Long, override val name: String, override val country: String ) : Player }
52. Surface.kt: enum class Surface { OUTDOOR_HARD, INDOOR_HARD, GRASS, CLAY } Tournament.sq: CREATE TABLE tournament ( id INTEGER NOT NULL PRIMARY KEY, name TEXT NOT NULL, surface TEXT AS Surface NOT NULL, year INTEGER NOT NULL ); Tournament.sq: CREATE TABLE tournament ( id INTEGER NOT NULL PRIMARY KEY, name TEXT NOT NULL, surface TEXT AS Surface NOT NULL, year INTEGER NOT NULL );
53. build/Tournament.sq: interface Tournament { val id: Long val name: String val surface: Surface val year: Long class Adapter( internal val surfaceAdapter: ColumnAdapter<Surface, String> ) data class Impl( override val id: Long, override val name: String, override val surface: Surface, override val year: Long ) : Tournament } build/Tournament.sq: interface Tournament { val id: Long val name: String val surface: Surface val year: Long class Adapter( internal val surfaceAdapter: ColumnAdapter<Surface, String> ) data class Impl( override val id: Long, override val name: String, override val surface: Surface, override val year: Long ) : Tournament } build/Tournament.sq: interface Tournament { val id: Long val name: String val surface: Surface val year: Long class Adapter( internal val surfaceAdapter: ColumnAdapter<Surface, String> ) data class Impl( override val id: Long, override val name: String, override val surface: Surface, override val year: Long ) : Tournament }
54. com.squareup.sqldelight:runtime:1.0.0 interface ColumnAdapter<T : Any, S> { fun decode(databaseValue: S): T fun encode(value: T): S }
55. com.squareup.sqldelight:runtime:1.0.0 class EnumColumnAdapter<T : Enum<T>> inline fun <reified T : Enum<T>> EnumColumnAdapter() : EnumColumnAdapter<T> { return EnumColumnAdapter(enumValues()) }
56. src/YourCode.kt: val queryWrapper = QueryWrapper( database = database, tournamentAdapter = Tournament.Adapter( surfaceAdapter = EnumColumnAdapter()A )A ) src/YourCode.kt: val queryWrapper = QueryWrapper( database = database, tournamentAdapter = Tournament.Adapter( surfaceAdapter = EnumColumnAdapter()A )A )
57. com.squareup.sqldelight:runtime:1.0.0 interface SqlDatabase { fun getConnection(): SqlDatabaseConnection fun close() }
58. db app Tennis
59. db app Tennis
60. db app db:android
61. db apply plugin: 'org.jetbrains.kotlin.platform.common' apply plugin: 'com.squareup.sqldelight'
62. db expect class DatabaseFactory { fun create(): SqlDatabase }
63. db app db:android
64. apply plugin: 'com.android.library' apply plugin: 'kotlin-platform-android' dependencies { expectedBy project(':db') implementation “com.squareup.sqldelight:android-driver:1.0.0-alpha5” } db:android
65. db:android actual class DatabaseFactory( private val context: Context ) { actual fun create(): SqlDatabase { return QueryWrapper.create(context, "tennis.db") } }
66. db app db:android
67. db fun QueryWrapper.Helper.create( databaseFactory: DatabaseFactory ): QueryWrapper { val queryWrapper = QueryWrapper( database = databaseFactory.create(), tournamentAdapter = Tournament.Adapter( surfaceAdapter = EnumColumnAdapter() ) ) }
68. db app db:android
69. val queryWrapper = QueryWrapper.create(DatabaseFactory(this)) app
70. val queryWrapper = QueryWrapper.create(DatabaseFactory(this)) queryWrapper.playerQueries.insert( id = 1, name = "Novak Djokovic", country = "Serbia" ) app
71. db app db:android
72. db app db:android iosApp db:native
73. db:native apply plugin: ‘kotlin-platform-native’ dependencies { expectedBy project(‘:db') implementation “co.touchlab.knarch:knarch:0.7-alpha4" implementation "com.squareup.sqldelight:sqldelightruntimeios" implementation "com.squareup.sqldelight:sqldelightmultiplatformdriverios" }
74. actual class DatabaseFactory { actual fun create(): SqlDatabase { val context = DefaultSystemContext() val factory = IosNativeOpenHelperFactory(context) return QueryWrapper.create( name = "tennis.db", openHelperFactory = factory ) } } db:native
75. db app db:android iosApp db:native
76. iosApp let database = DbQueryWrapperHelper().create( databaseFactory: DbDatabaseFactory() )A
77. let database = DbQueryWrapperHelper().create( databaseFactory: DbDatabaseFactory() )A database.playerQueries .insert( id: 1, name: "Novak Djokovic", country: "Serbia" ) iosApp
78. db app db:android iosApp db:native
79. db val federer = 3L queryWrapper.playerQueries.insert( id = federer, name = "Roger Federer", country = "Switzerland" ) insert: INSERT INTO player (id, name, country) VALUES (?, ?, ?);
80. db CREATE TABLE match ( tournament INTEGER NOT NULL REFERENCES tournament, player1 INTEGER NOT NULL REFERENCES player, player2 INTEGER NOT NULL REFERENCES player, winner INTEGER NOT NULL REFERENCES player, CHECK (winner == player1 OR winner == player2), CHECK (player1 <> player2), PRIMARY KEY (player1, player2, tournament) );
81. db queryWrapper.tournamentQueries.insert( id = 2, name = "ATP World Tour Masters 1000 Miami", surface = OUTDOOR_HARD, year = 2017 ) queryWrapper.matchQueries.insert( tournament = 2, player1 = rafa, player2 = federer, winner = federer )
82. db headToHead: SELECT player1.name AS player1Name, player2.name AS player2Name, count(nullif(match.winner = player1.id, 0)) AS player1Wins, count(nullif(match.winner = player2.id, 0)) AS player2Wins FROM match JOIN player AS player1 ON (player1.name = :firstPlayerName AND (player1.id = match.player1 OR player1.id = match.player2) ) JOIN player AS player2 ON (player2.name = :secondPlayerName AND (player2.id = match.player1 OR player2.id = match.player2) ) ;
83. Match.sq: headToHead: SELECT ... db build/HeadToHead.kt: interface HeadToHead { val player1Name: String val player2Name: String val player1Wins: Long val player2Wins: Long }
84. Match.sq: headToHead: SELECT ... db build/MatchQueries.kt: class MatchQueries { fun headToHead( firstPlayerName: String, secondPlayerName: String ): Query<HeadToHead> }
85. Match.sq: headToHead: SELECT ... db build/MatchQueries.kt: class MatchQueries { fun <T : Any> headToHead( firstPlayerName: String, secondPlayerName: String, mapper: ( player1Name: String, player2Name: String, player1Wins: Long, player2Wins: Long ) -> T ): Query<T>
86. com.squareup.sqldelight:runtime:1.0.0 open class Query<out RowType : Any> { fun addListener(listener: Listener) fun removeListener(listener: Listener) fun executeAsList(): List<RowType> fun executeAsOne(): RowType fun executeAsOneOrNull(): RowType? interface Listener { fun queryResultsChanged() } } com.squareup.sqldelight:runtime:1.0.0 open class Query<out RowType : Any> { fun addListener(listener: Listener) fun removeListener(listener: Listener) fun executeAsList(): List<RowType> fun executeAsOne(): RowType fun executeAsOneOrNull(): RowType? interface Listener { fun queryResultsChanged() } }
87. db backend protos api presenters viewmodel + viewevent app interface InstrumentManager { @CheckResult fun withToken( token: String ): Observable<Instrument> }
88. iosApp db:native db app db:android
89. iosApp db:native db app db:android
90. com.squareup.sqldelight:rxjava2-extensions:1.0.0 fun <T : Any> Query<T>.asObservable( scheduler: Scheduler = Schedulers.io() ) : Observable<Query<T>>
91. com.squareup.sqldelight:rxjava2-extensions:1.0.0 fun <T : Any> Query<T>.asObservable( scheduler: Scheduler = Schedulers.io() ) : Observable<Query<T>> fun <T : Any> Observable<Query<T>>.mapToOne(): Observable<T> fun <T : Any> Observable<Query<T>>.mapToOneOrDefault( defaultValue: T ) : Observable<T> fun <T : Any> Observable<Query<T>>.mapToOptional() : Observable<Optional<T>> fun <T: Any> Observable<Query<T>>.mapToList(): Observable<List<T>> fun <T : Any> Observable<Query<T>>.mapToOneNonNull(): Observable<T>
92. iosApp db:native db app db:android
93. implementation “com.squareup.sqldelight:rxjava2-extensions:1.0.0-alpha5” app
94. app queryWrapper.matchQueries.headToHead("Roger Federer", "Rafael Nadal") .asObservable(Schedulers.io()) .mapToList()
95. iosApp db:native db app db:android
96. iosApp struct HeadToHead { var player1Name: String var player2Name: String var player1Wins: NSNumber var player2Wins: NSNumber }
97. iosApp func createHeadToHead( player1Name: String, player2Name: String, player1Wins: NSNumber, player2Wins: NSNumber ) -> HeadToHead { return HeadToHead( player1Name: player1Name, player2Name: player2Name, player1Wins: player1Wins, player2Wins: player2Wins ) }
98. iosApp let headToHead = (database.matchQueries .headToHead( firstPlayerName: "Rafael Nadal", secondPlayerName: "Roger Federer", mapper: createHeadToHead ) .executeAsOne() as! HeadToHead)
99. iosApp let headToHead = (database.matchQueries .headToHead( firstPlayerName: "Rafael Nadal", secondPlayerName: "Roger Federer", mapper: createHeadToHead ) .executeAsOne() as! HeadToHead)
100. iosApp db:native db app db:android
101. db class QueryTests { @Test fun headToHeadTest() { val headToHead = queryWrapper.matchQueries.headToHead( firstPlayerName = "Rafael Nadal", secondPlayerName = "Roger Federer" ).executeAsOne() assertEquals(headToHead.player1Name, "Rafael Nadal") assertEquals(headToHead.player1Wins, 23) assertEquals(headToHead.player2Name, "Roger Federer") assertEquals(headToHead.player2Wins, 15) } }
102. SqlDelight 1.0 (alpha)
103. Migrations
104. Migrations CREATE TABLE player ( id INTEGER NOT NULL PRIMARY KEY, name TEXT NOT NULL, country TEXT NOT NULL );
105. Migrations CREATE TABLE player ( id INTEGER NOT NULL PRIMARY KEY, name TEXT NOT NULL, country TEXT NOT NULL, ranking INTEGER NOT NULL );
106. Migrations CREATE TABLE player ( id INTEGER NOT NULL PRIMARY KEY, name TEXT NOT NULL, country TEXT NOT NULL, ranking INTEGER NOT NULL ); Execution failed for task ':db:verifySqlDelightMigration'. > Error migrating from 1.db, fresh database looks different from migration database: /tables[player]/columns[player.ranking] - ADDED
107. Migrations 1.sqm: ALTER TABLE player ADD COLUMN ranking INTEGER NOT NULL DEFAULT 0;
108. Shorthands Tournament.sq: insertTournament: INSERT INTO tournament VALUES ?; build/TournamentQueries.sq: class TournamentQueries() { fun insertTournament(tournament: Tournament): Long }
109. Shorthands Tournament.sq: selectForSurface: SELECT * FROM tournament WHERE surface IN ?; build/TournamentQueries.sq: class TournamentQueries() { fun selectForSurface( surface: Collection<Surface> ): Query<Tournament> }
110. Testing dependencies { implementation “com.squareup.sqldelight:android-driver:1.0.0-alpha5” testImplementation “com.squareup.sqldelight:sqlite-driver:1.0.0-alpha5” }
111. Testing dependencies { implementation “com.squareup.sqldelight:android-driver:1.0.0-alpha5” testImplementation “com.squareup.sqldelight:sqlite-driver:1.0.0-alpha5” } val database = SqliteJdbcOpenHelper() QueryWrapper.Helper.onCreate(database.getConnection())
112. viewmodel + viewevent app api presenters protos backend db
113. viewmodel + viewevent app api presenters protos backend db: android db
114. viewmodel + viewevent app api presenters protos backend db: android db
115. protos Wire protobufs parcelable
116. protos protobufs parcelable
117. protos parcelable
118. protos
119. viewmodel + viewevent app api presenters protos backend db: android db
120. viewmodel + viewevent app api presenters protos backend db: android db
121. viewmodel + viewevent app api presenters protos backend db: android db
122. viewmodel + viewevent app api presenters protos backend db: android db
126. alec strong @strongolopolis