JarCasting
Realm is a mobile database that runs directly inside phones, tablets or wearables. This repository holds the source code for the Kotlin SDK for Realm, which runs on Kotlin Multiplatform and Android.
Quick Startup
Prerequisite
Start a new KMM project.
Setup
- Add the following Gradle configuration in the root project (make sure you're using Kotlin
1.4.20or recent)<root project>/build.gradle.kts
buildscript {
repositories {
// other repo
maven(url = "https://oss.jfrog.org/artifactory/oss-snapshot-local")
}
dependencies {
classpath("org.jetbrains.kotlin:kotlin-gradle-plugin:1.4.20")// minimum 1.4.20
classpath("com.android.tools.build:gradle:4.0.1")
classpath("io.realm.kotlin:gradle-plugin:0.0.1-SNAPSHOT")
}
}
allprojects {
repositories {
// other repo
maven(url = "https://oss.jfrog.org/artifactory/oss-snapshot-local")
}
}
- Apply the
realm-kotlinplugin and specify the dependency in the common source set.
See Config.kt for the latest version number.
plugins {
kotlin("multiplatform")
id("com.android.library")
id("realm-kotlin")
}
kotlin {
sourceSets {
val commonMain by getting {
dependencies {
implementation("io.realm.kotlin:library:0.0.1-SNAPSHOT")
}
}
}
Define model
Start writing your shared database logic in the shared module by defining first your model
class Person : RealmObject {
var name: String = "Foo"
var dog: Dog? = null
}
class Dog : RealmObject {
var name: String = ""
var age: Int = 0
}
Open Database
Define a RealmConfiguration with the database schema, then open the Realm using it.
val configuration = RealmConfiguration(schema = setOf(Person::class, Dog::class))
val realm = Realm.open(configuration)
Write
Persist some data by instantiating the data objects and copying it into the open Realm instance
// plain old kotlin object
val person = Person().apply {
name = "Carlo"
dog = Dog().apply { name = "Fido"; age = 16 }
}
// persist it in a transaction
realm.beginTransaction()
val managedPerson = realm.copyToRealm(person)
realm.commitTransaction()
// alternatively we can use
realm.beginTransaction()
realm.create<Person>().apply {
name = "Bar"
dog = Dog().apply { name = "Filo"; age = 11 }
}
realm.commitTransaction()
Query
The query language supported by Realm is inspired by Apple’s NSPredicate, see more examples here
// All Persons
val all = realm.objects<Person>()
// Person named 'Carlo'
val filteredByName = realm.objects<Person>().query("name = $0", "Carlo")
// Person having a dog aged more than 7 with a name starting with 'Fi'
val filteredByDog = realm.objects<Person>().query("dog.age > $0 AND dog.name BEGINSWITH $1", 7, "Fi")
Update
// Find the first Person without a dog
realm.objects<Person>().query("dog == NULL LIMIT(1)")
.firstOrNull()
?.also { personWithoutDog ->
// Add a dog in a transaction
realm.beginTransaction()
personWithoutDog.dog = Dog().apply { name = "Laika"; age = 3 }
realm.commitTransaction()
}
Delete
Use the result of a query to delete from the database
// delete all Dogs
realm.beginTransaction()
realm.objects<Dog>().delete()
realm.commitTransaction()
Next: head to the full KMM example.
NOTE: The SDK doesn't currently support x86 - Please use an x86_64 or arm64 emulator/device
Developer Preview
The Realm Kotlin SDK is in Developer Preview. All API's might change without warning and no guarantees are given about stability. Do not use in production.
Design documents
The public API of the SDK has not been finalized. Design discussions will happen in both Google Doc and this Github repository. Most bigger features will first undergo a design process that might not involve code. These design documents can be found using the following links:
How to build locally:
Prerequisites
- Swig. On Mac this can be installed using Homebrew:
brew install swig. - CMake 3.18.1. Can be installed through the Android SDK Manager.
Commands to build from source
git submodule update --init --recursive
cd packages
./gradlew assemble
In Android Studio open the test project, which will open also the realm-library and the compiler projects
You can also run tests from the commandline:
cd test
./gradlew connectedAndroidTest
./gradlew macosTest
Using Snapshots
If you want to test recent bugfixes or features that have not been packaged in an official release yet, you can use a -SNAPSHOT release of the current development version of Realm via Gradle, available on JFrog OSS
// Global build.gradle
buildscript {
repositories {
google()
jcenter()
maven {
url 'http://oss.jfrog.org/artifactory/oss-snapshot-local'
}
maven {
url 'https://dl.bintray.com/kotlin/kotlin-dev'
}
}
dependencies {
classpath 'io.realm.kotlin:plugin-gradle:<VERSION>'
}
}
allprojects {
repositories {
google()
jcenter()
maven {
url 'http://oss.jfrog.org/artifactory/oss-snapshot-local'
}
maven {
url 'https://dl.bintray.com/kotlin/kotlin-dev'
}
}
}
See Config.kt for the latest version number.
Repository Guidelines
Branch Strategy
We have three branches for shared development: master, releases and next-major. Tagged releases are only made from releases.
master:
- Target branch for new features.
- Cotains the latest publishable state of the SDK.
- SNAPSHOT releases are being created for every commit.
releases:
- All tagged releases are made from this branch.
- Target branch for bug fixes.
- Every commit should be merged back to master
master. - Minor changes (e.g. to documentation, tests, and the build system) may not affect end users but should still be merged to
releasesto avoid diverging too far frommasterand to reduce the likelihood of merge conflicts.
next-major:
- Target branch for breaking changes that would result in a major version bump.
Note: We currently only have the master branch, as no tagged releases have been made yet.
Code Style
We use the offical style guide from Kotlin which is enforced using ktlint and detekt.
# Call from root folder to check if code is compliant.
./gradlew ktlintCheck
./gradlew detekt
# Call from root folder to automatically format all Kotlin code according to the code style rules.
./gradlew ktlintFormat
Note: ktlint does not allow group imports using .*. You can configure IntelliJ to disallow this by going to preferences Editor > Code Style > Kotlin > Imports and select "Use single name imports".
Writing Tests
Currently all unit tests should be place in the test/ project instead of packages/library. The reason for this is that we need to apply the Realm Compiler Plugin to the tests and this introduces a circular dependency if the tests are in library.
Inside tests/ there are 3 locations the files can be placed in:
test/src/commonTesttest/src/androidTesttest/src/macosTest
Ideally all shared tests should be in commonTest with specific platform tests in androidTest/macosTest. However IntelliJ does not yet allow you run you to run common tests on Android from within the IDE](https://youtrack.jetbrains.com/issue/KT-46452), so we are using the following work-around:
-
All "common" tests should be placed in the
test/src/androidtest/kotlin/io/realm/sharedfolder. They should be written using only common API's. I'e. use Kotlin Test, not JUnit. Thisio.realm.sharedpackage should only contain tests we plan to eventually move tocommontTest. -
When adding a new test file to
androidTestwe need to re-create the symlinks for macOS. This can be done, using the following command on Mac:
cd test/src/macosTest/kotlin/io/realm/shared
ln -sf ../../../../../androidTest/kotlin/io/realm/shared/* ./
-
Both the real test file and the symlink must be committed to Git.
-
This allows us to run and debug unit tests on both macOS and Android. It is easier getting the imports correctly using the macOS sourceset as the Android code will default to using JUnit.
All platform specific tests should be placed outside the io.realm.shared package, the default being io.realm.
Defining dependencies
All dependency versions and other constants we might want to share between projects are defined inside the file buildSrc/src/main/kotlin/Config.kt. Any new dependencies should be added to this file as well, so we only have one location for these.
Contributing Enhancements
We love contributions to Realm! If you'd like to contribute code, documentation, or any other improvements, please file a Pull Request on our GitHub repository. Make sure to accept our CLA!
This project adheres to the Contributor Covenant Code of Conduct. By participating, you are expected to uphold this code. Please report unacceptable behavior to [email protected].
CLA
Realm welcomes all contributions! The only requirement we have is that, like many other projects, we need to have a Contributor License Agreement (CLA) in place before we can accept any external code. Our own CLA is a modified version of the Apache Software Foundation’s CLA.
Please submit your CLA electronically using our Google form so we can accept your submissions. The GitHub username you file there will need to match that of your Pull Requests. If you have any questions or cannot file the CLA electronically, you can email [email protected].
Samples
Kotlin Multiplatform Sample
The folder examples/kmm-sample contains an example showing how to use Realm in a multiplatform project, sharing code for using Realm in the shared module. The project is based on https://github.com/Kotlin/kmm-sample.
