Core concepts

Sources and consumers

MVICore works with sources and consumers of observable data at its heart.

That is:

• outputs are of type ObservableSource<T>
• inputs are of type Consumer<T>

Stores

The Store<Wish, State> interface defines the outline of a state machine that - can receive objects of type Wish on its input - can produce objects of type State on its output - in addition, it holds on to the latest State, which can be queried without subscribing to the Store

interface Store<Wish : Any, State : Any> : Consumer<Wish>, ObservableSource<State> {

    val state: State
}

State is meant to be immutable, for which we'll use Kotlin data classes.

Features

A Feature is a Store with the addition of:

• being Disposable, as it might hold subscriptions
• being a source of News

interface Feature<Wish : Any, State : Any, News: Any> : Store<Wish, State>, Disposable {

    val news: ObservableSource<News>
}

News marks the type of the events a Feature can emit. These are pieces of information you don’t want to store in the state, just fire off once when they happen.

More about that in the chapter Events that should be consumed only once.

Features are hot observables

Features are not cold observables: they do not wait for subscriptions to start working, and they are not scoped by subscriptions to them. They are push-based (pushing out new states automatically) and not pull-based (producing something upon a subscription).

This is a designed feature of the library.

Features are supposed to be able to be active in the background, and have possibly many, differently scoped inputs / outputs to them.

Two things follow from this:

1. A Feature starts working immediately on creation, and emits its initial state.
2. A Feature always needs to be disposed of when its lifecycle should end. That means it's your responsibility to call .dispose() on it, so that any asynchronous jobs still executing are properly disposed of.

Bottom line

Don't forget to call .dispose() at the end of the Feature's lifecycle