UseKase
Provides default UseCase implementations for the Clean Architecture
Description
UseKase is a Kotlin library which provides a set of default implementations of UseCases. Most of the UseCases depend on heavily on RxJava2.
I found my self copying these implementations in new projects again and again. Even if these contain only some lines of code it was just annoying. So I decided to create this library which provides these for me.
Because all Kotlin classes are final by default I created for each UseCase a typealias to the correct interface. This make the UseCase in Presenters testable. Because it was as annoying as copying and pasting the UseCase implementations I created an annotation processor which creates the typealias at runtime for me. You can find the code for that in the usekase-processor module.
How to use it
Get the dependencies
UseKase is available via jcenter:
repositories {
jcenter()
}
dependencies {
implementation("guru.stefma.cleancomponents:usekase:$useKaseVersion")
// Alternatively (but highly recommended): usekase-processor
kapt("guru.stefma.cleancomponents:usekase-processor:$useKaseVersion")
}Configurate the sourceSet
First you have to add the generated source dir to your sourceSet.
You can do this by adding the following into your build.gradle file:
// Add the generated source as sourceSet
android.applicationVariants.all { variant ->
variant.addJavaSourceFoldersToModel()
def kotlinGenerated = file("$buildDir/generated/source/kaptKotlin/${variant.name}")
variant.addJavaSourceFoldersToModel(kotlinGenerated)
}For pure Kotlin projects the syntax is a little bit different. See this issue for more.
Create a UseCase
You can just implement one of the provided default UseCase implementations
and add the @UseCase annotation to it:
@UseCase
GetUserUseCase(
override val executionScheduler: Scheduler = Schedulers.io(),
override val postExecutionScheduler: Scheduler = AndroidSchedulers.mainThread(),
private val api: BackendApi
) : SingleUseCase<User, String> {
override fun buildUseCase(params: String): Single<User> {
return api.getUserByUserId(params)
}
}If the UseKase-Processor is applied it will generated the following typealias:
typealias GetUser = SingleUseCase<User, String>All available UseCase implementations are:
UseCase<R, P>RxUseCase<R, P>SingleUseCase<R, P>FlowableUseCase<R, P>ObservableUseCase<R, P>MaybeUseCase<R, P>CompletableUseCase<P>
Kotlin coroutine version
The usekase-coroutines module offers a base use case class CoroutineUseCase that you can extend:
@UseCase
class GetUserCoroutineUseCase(
override val callbackDispatcher: CoroutineContext = Dispatchers.IO
) : CoroutineUseCase<User, GetUserCoroutineUseCase.Params>() {
override suspend fun execute(params: Params): Result<User> {
return Result.success(User(params.userId, "Thorsten", MALE, Random().nextInt(1000).toString()))
}
data class Params(val userId: String)
}You have to execute it from a CoroutineScope like this:
GlobalScope.launch {
getUserCoroutine(
onFailure = { },
onError = { }
)
}However, the module currently uses the experimental Result class as a return type. You need to enable this first
by putting this in your build.gradle.kts:
tasks.withType(KotlinCompile::class.java).configureEach {
kotlinOptions.apply {
jvmTarget = "1.8"
freeCompilerArgs = listOf("-Xallow-result-return-type")
}
}
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