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"

Contents

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.

Authors

• Damiano Giusti
• MOLO17 Srl