Anatomy

Type Rx.Reactive is the base type of reactives, with this signature:

type Reactive<T> = {
    // Listen for values or messages
    on(handler: ((value: Passed<T>) => void)): Unsubscriber
    // Listen for values
    onValue(handler: ((value: T) => void)): Unsubscriber
    // Some reactives allow setting values
    set?(value: T): void
    // Close the reactive, rendering it unusable
    dispose(reason: string): void
    // Check if the reactive is disposed
    isDisposed(): boolean
}

Consuming

For the most part, you’ll use onValue to listen for data emitted by the reactive. If you use on, you’ll get the data and also signalling messages, for example when the reactive completes or there’s an error.

rx.onValue(value => {
    // value of reactive has changed
})

Unsubscribing

Both on and onValue return type Unsubscriber, which is just a function to call to remove the subscription. Use this when you want to keep the source alive, but no longer want to receive values.

const rxOff = rx.onValue(handler);

// Later, call the provided unsubscribe function:
rxOff();

Setting values

Only Type Rx.ReactiveWritable reactives support the set function. This allows you to set a value to the stream, which is then emitted at the on and onValue events.

You can use Rx.isWritable to check if set is supported.

Some types of reactives provide bespoke functions for changing values. For example when using Rx.From.object, you get an updateField function for changing the value of a named field.