Skip to content


BundleSpec to use Bundle with property syntax for Intent extras and more.

Supported platforms: Android.


If you want to use this dependency without using one of the fun packs, you can use Splitties.bundle, provided you have refreshVersions added to the project.

For reference, the maven coordinates of this module are com.louiscad.splitties:splitties-bundle.

Non-exhaustive list of use cases

  • Intent extras of Activities, BroadcastReceivers, Services, etc.
  • Instance state of Activities, Fragments and Views.

Can be used for Activity extras, but also in Service extras, BroadcastReceiver and other parts where an Intent or a Bundle is used.


For Activity extras

  1. Let's say you have an Activity subclass named YourActivity.
  2. In YourActivity, add a nested object named ExtrasSpec.
  3. Make it extend BundleSpec.
  4. For each required Intent extra you need, in ExtrasSpec, add a var property with explicit non null type, delegated by bundle().
  5. For each optional Intent extra you need, still in ExtrasSpec, add a var property with either and explicit nullable type, delegated by bundleOrNull(), or with a non null type, delegated by bundleOrDefault(…) or by bundleOrElse { … }.
  6. When setting up the Intent to start your Activity, call putExtras(YourActivity.ExtrasSpec) { … } on it, setting values on the ExtrasSpec properties in the lambda.
  7. From YourActivity, call withExtras(ExtrasSpec) { … } to get the extras as properties from the lambda (the result of the call is the result of the lambda).

Other usages

Only Activity has a withExtras(…) { … } extension, but you can use with(…) { … } extension on any Bundle and any Intent extras.

The putExtras(…) { … } extension works on any Intent, Activity or not.

See the examples below.

Important details

See the implementation of the put(…) extension on Bundle to check all the supported types (it is likely to suit your needs).

You may only access the delegated properties of a BundleSpec subclass inside the withExtras(…) { … } lambda or inside the someBundle.with(…) { … } lambda. If you violate this rule, an IllegalStateException will be thrown.

The implementation has been optimized for efficiency. The delegates under bundle() and bundleOrNull() are singletons and are shared for all properties app-wide. The versions that accept a key or a default value can't be singletons, but since you're likely using them in object backed specs, they are instantiated only once per property, having a minimal memory impact (especially when compared to the cost of data serialization in Bundles).


Extras in an Activity

class DemoActivity : AppCompatActivity() {

    object ExtrasSpec : BundleSpec() {
        var userName: String by bundle() // Required extra
        var showGreetingToast by bundleOrDefault(false) // Optional extra, defaults to false
        var optionalExtra: String? by bundleOrNull() // Optional extra

    override fun onCreate(savedInstanceState: Bundle?) {
        withExtras(ExtrasSpec) { // Populates ExtrasSpec with actual extras
            if (showGreetingToast) toast(android.R.string.ok)
            optionalExtras?.forEach {
                Timber.i("Character from optional extra: $it")

class StartDemoActivity : AppCompatActivity() {

    private fun someFunction(name: String, isUserPolite: Boolean = false) {
        startActivity(Intent(this, {
            putExtras(DemoActivity.ExtrasSpec) {
                userName = name
                showGreetingToast = isUserPolite

Extras in a BroadcastReceiver

class AirplaneModeReceiver : BroadcastReceiver() {

    object ExtrasSpec : BundleSpec() {
        var isAirplaneModeOn: Boolean by bundle("state")

    override fun onReceive(context: Context, intent: Intent) {
        if (intent.action != Intent.ACTION_AIRPLANE_MODE_CHANGED) return
        val isAirplaneModeOn = intent.extras.with(ExtrasSpec) { isAirplaneModeOn }

Instance State in an Activity

class DemoActivity : AppCompatActivity() {

    private object InstanceStateSpec : BundleSpec() {
        var startTime: Long by bundle()

    private var startTimestamp = 0L

    override fun onCreate(savedInstanceState: Bundle?) {
        startTimestamp = savedInstanceState?.with(InstanceStateSpec) {
        } ?: System.currentTimeMillis()

    override fun onSaveInstanceState(outState: Bundle) {
        outState.with(InstanceStateSpec) {
            startTime = startTimestamp