Context Isolation

What is Context Isolation?

For SDK Makers, you can also work with Koin in a non-global way: use Koin for the DI of your library and avoid any conflict by people using your library and Koin by isolating your context.

In a standard way, we can start Koin like that:

// start a KoinApplication and register it in Global context
startKoin {

    // declare used modules
    modules(...)
}

This uses the default Koin context to register your dependencies.

But if we want to use an isolated Koin instance, you need to declare an instance and store it in a class to hold your instance. You will have to keep your Koin Application instance available in your library and pass it to your custom KoinComponent implementation:

The MyIsolatedKoinContext class is holding our Koin instance here:

// Get a Context for your Koin instance
object MyIsolatedKoinContext {

    private val koinApp = koinApplication {
        // declare used modules
        modules(coffeeAppModule)
    }

    val koin = koinApp.koin 
}

Let's use MyIsolatedKoinContext to define our IsolatedKoinComponent class, a KoinComponent that will use our isolated context:

internal interface IsolatedKoinComponent : KoinComponent {

    // Override default Koin instance
    override fun getKoin(): Koin = MyIsolatedKoinContext.koin
}

Everything is ready, just use IsolatedKoinComponent to retrieve instances from isolated context:

class MyKoinComponent : IsolatedKoinComponent {
    // inject & get will target MyKoinContext
}

Testing

To test classes that are retrieving dependencies with by inject() delegate override getKoin() method and define custom Koin module:

class MyClassTest : KoinTest {
    // Koin Context used to retrieve dependencies
    override fun getKoin(): Koin = MyIsolatedKoinContext.koin

    @Before
    fun setUp() {
       // Define custom Koin module
        val module = module {
            // Register dependencies
        }

        koin.loadModules(listOf(module))
    }
}