How to Use KStore
Create your store
Initialise your stores and keep a reference to it in your app (preferably using DI so that they are reused)
KStore File
val store: KStore<Pet> = storeOf(file = Path("$appDir/my_cats.json"))
KStore Storage
val store: KStore<Pet> = storeOf(key = "my_cats")
Other configuration options
Everything you want is in factory methods
val store: KStore<Pet> = storeOf(
// For kstore-file with json
file = Path("$appDir/$fileName.json"),
// Or for kstore-storage
key = "$keyName",
storage = localStorage, // optional
// Or your own custom codec
codec = YourCustomCodec<Pet>(), // optional
// Returns this value if the file is not found. Defaults to null
default = null, // optional
// Maintain a cache. If set to false, it always reads from disk
enableCache = true, // optional
// For versioning
version = 0, // optional
migration = { version, jsonElement -> default }, // optional
// For kstore-file, the serializer to use.
serializer = Json {
ignoreUnknownKeys = true
encodeDefaults = true
}, // optional
)
You can also use binary codecs for storage (e.g. Protobuf, Cbor)
// Boilerplate implementation for a BinaryCodec
public class BinaryCodec<T : @Serializable Any>(
private val key: String,
private val format: BinaryFormat,
private val serializer: KSerializer<T>,
private val storage: Storage,
) : Codec<T> {
override suspend fun encode(value: T?) {
if (value != null) storage[key] = format.encodeToByteArray(serializer, value)
else storage.remove(key)
}
override suspend fun decode(): T? = storage[key]
?.let { format.decodeFromByteArray(serializer, it) }
}
// Protobuf implementation
public inline fun <reified T : @Serializable Any> ProtobufCodec(
key: String,
// Other formats can be found here: https://kotlinlang.org/api/kotlinx.serialization/
format: BinaryFormat = Protobuf,
storage: Storage = localStorage,
): BinaryCodec<T> = BinaryCodec(
key = key,
format = format,
serializer = format.serializersModule.serializer(),
storage = storage,
)
// Use the `Codec` to create a store
val store = KStore<Pet> = storeOf(
codec = ProtobufCodec<Pet>,
default = Pet(),
enableCache = true
)
Use your store
Given that you have a @Serializable model and a value
@Serializable data class Pet(val name: String, val age: Int) // Any serializable
val mylo = Pet(name = "Mylo", age = 1)
Get value
Get a value once
val mylo: Pet? = store.get()
Or observe for changes
val pets: Flow<Pet?> = store.updates
Set value
store.set(mylo)
Update a value
store.update { pet: Pet? ->
pet?.copy(age = pet.age + 1)
}
Delete/Reset value
store.delete()
You can also reset a value back to its default (if set, see here)
store.reset()
Last modified: 20 August 2025