Bootstrappers¶

Listening to remote sources¶

So far all of the triggers to our Features were internal:

Wishes come from client code
Actions are triggered inside Feature in the PostProcessor

But what if you need to react to let's say when the server sends you a push? You can of course listen to them outside of your Feature and then push Wishes, but this has its own disadvantages:

Part of your business logic is now living outside of your class. If you are passing your component around for others to use, everyone will need to pay attention how to set it up. This is not correct.
From outside you can only trigger public Wishes, not Actions

The Bootstrapper is solving exactly these problems.

Bootstrapper¶

It's defined as:

typealias Bootstrapper<Action> = () -> Observable<Action>

which practically means, that when invoked, it can give you a stream of Actions. You can use this interface to add initial wiring to your Feature:

class BootstrapperImpl : Bootstrapper<Action> {
    private val service1: Observable<Any> = TODO()
    private val service2: Observable<Any> = TODO()

    override fun invoke(): Observable<Action> = Observable.merge<Action>(
        service1.map { InvalidateCache },
        service2.map { ReloadSomething }
    ).observeOn(AndroidSchedulers.mainThread())
}

Pass your Bootstrapper implementation in the constructor to either ReducerFeature, ActorReducerFeature, or BaseFeature:

class MyComplexFeature : BaseFeature<Wish, Action, Effect, State, News>(
    // ...remainder omitted...
    bootstrapper = BootstrapperImpl()
)

The implementation of BaseFeature wires it up for you.

Bootstrapping is immediate by default¶

As noted in the core concepts section, Features are essentially hot observables. It's worth to repeat this here, because there's an important aspect of it here: Bootstrapper is invoked immediately on Feature creation and by default will not wait for anything else.

You can picture the Feature as if it was a glorified BehaviourSubject: when you create that with createDefault, it emits its first state straight away and continues to emit whatever is put into it after creation.

Delaying bootstrapping¶

If you need to delay bootstrapping for any reason, you can refer to the corresponding best practices section: delaying bootstrapping