Couchbase Lite Kotlin

Kotlin-friendly extensions for Couchbase Lite Android and Java SDKs.

Proudly made by MOLO17 Srl 🚀

Kotlin extensions for Couchbase Lite

Couchbase Lite Kotlin is a lightweight library that adds convenient extension functions to Couchbase Lite Android and Java SDKs.

This library introduces a lightweight wrapper on top of N1QL query language, Document creation and much more. Also, it provides support for a more fluent listener API, introducing first-class support for Kotlin Coroutines and the Flow API.

Installing

Add JitPack as repository for your project:

allprojects {
    repositories {
        ...
        maven { url "https://jitpack.io" }
    }
}

And then to your module build.gradle file:

implementation "com.github.MOLO17.couchbase-lite-kotlin:kotlin:1.3.0"

For Android use

implementation "com.github.MOLO17.couchbase-lite-kotlin:android-ktx:1.3.0"

Here are the main features that Couchbase Lite Kotlin provides for boosting the integration of the Couchbase Lite SDK with Kotlin.

QueryBuilder extensions
Document builder DSL
Query Flow support
ResultSet model mapping
Database extensions
Replicator extensions

QueryBuilder extensions

Syntax for building a query has gone more straight-forward thanks to the infix function support.

select(all()) from database where { "type" equalTo "user" }

Or just a bunch of fields:

select("name", "surname") from database where { "type" equalTo "user" }

You can even do more powerful querying:

select("name", "type")
  .from(database)
  .where { 
    ("type" equalTo "user" and "name" equalTo "Frederic") or
      ("type" equalTo "pet" and "name" like "Kitt") 
  }
  .orderBy { "name".ascending() }
  .limit(10)

Document builder DSL

For creating a new MutableDocument ready to be saved, you can now use a new Kotlin DSL:

val document = MutableDocument {
  "name" to "Frederic"
  "surname" to "Monti"
  "age" to 24
  "pets" to listOf("Kitty", "Kitten", "Kitto")
  "type" to "user"
}

database.save(document)

Query Flow support

Now Couchbase Lite queries become Flows. Couchbase Lite Kotlin ports the coroutines Flow stream API for observing Live Queries results.

select(all())
  .from(database)
  .where { "type" equalTo "user" }
  .asFlow()
  .collect { value: ResultSet -> 
    // consume ResultSet
  }

As plus, you receive automatic LiveQuery cancellation when the Flow tears down.

ResultSet model mapping

Thanks to Map delegation, mapping a ResultSet to a Kotlin class has never been so easy.

The library provides the ResultSet.toObjects() and Query.asObjectsFlow() (with android version Query.asKtxObjectsFlow()) extensions for helping to map results given a factory lambda.

Such factory lambda accepts a Map<String, Any?> and returns an instance of a certain type. Those requirements fits perfectly with a Map-delegated class.

class User(map: Map<String, Any?>) {
  val name: String by map
  val surname: String by map
  val age: Int by map
}

val users: List<User> = query.execute().toObjects(::User)

class User(map: Map<String, Any?>) {
  val name: String by map
  val surname: String by map
  val age: Int by map
}

val users: Flow<List<User>> = query.asObjectsFlow(::User)

Database extensions

As seen with the Query extensions, the Database has also been powered up.

You can now observe the DatabaseChange and DocumentChangeEvents using the Kotlin Flow API.

val changes: Flow<DatabaseChange> = database.changesFlow()
val documentChanges: Flow<DocumentChange> = database.documentChangesFlow(docId)

Also, a new useful syntax has been introduced when performing batch operations:

database.doInBatch {
  save(document)
  delete(otherDocument)
}

The Database is used as receiver in the specified lambda.

Replicator extensions

Replicator syntax has been boosted with the Kotlin Flow API. You can observe events using the following Flows:

val changesFlow: Flow<ReplicatorChange> = replicator.changesFlow()
val replicationFlow: Flow<DocumentReplication> = replicator.documentReplicationFlow()

In addition, for Android users, you can now bind the Replicator start() and stop() methods to be performed automatically when your Lifecycle-enabled component gets resumed or paused.

// Binds the Replicator to the Application lifecycle.

replicator.bindToLifecycle(ProcessLifecycleOwner.get().lifecycle)

// Binds the Replicator to the Activity/Fragment lifecycle.
{
    // inside an Activity or a Fragment ...

    replicator.bindToLifecycle(lifecycle)
}

That's it! Replicator will be automatically started when your component passes the ON_RESUME state, and it will be stopped when the component passes the ON_PAUSED state. As you may imagine, no further action will be made after the ON_DESTROY state.

MOLO17 / couchbase-lite-kotlin

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