Very simple DI for Android

BoilerplateDI.kt

class MyApplication : Application() {
    var dependencies: Dependencies = DefaultDependencies()
}

interface Dependencies {
    val thing: Thing
}

fun Activity.dependencies(): Dependencies {
    return (this.application as MyApplication).dependencies
}

class DefaultDependencies(
  override val thing = ThingImplementation()
}

BoilerplateDIMultiModule.kt

// App module

class MyApplication : Application(), OtherModuleDependencyProvider {
    var dependencies: Dependencies = DefaultDependencies()
    
    override val otherModuleDependencies = object : OtherModuleDependencies {
      override val thing = dependencies.thing
    }
}

interface Dependencies {
    val thing: Thing
}

fun Activity.dependencies(): Dependencies {
    return (this.application as MyApplication).dependencies
}

class DefaultDependencies(
  override val thing = ThingImplementation()
}

// Other module

interface OtherModuleDependencies {
  val thing: Thing
}

interface OtherModuleDependencyProvider {
  val otherModuleDependencies: OtherModuleDependencies
}

fun Activity.dependencies(): OtherModuleDependencies {
    return (this.application as OtherModuleDependencyProvider).otherModuleDependencies
}