ople


Event-driven, observable data flow for React 💥👀

Usage

The createOple function constructs an Ople object, which is both observable
and readonly to React components. Expose methods for React components to call,
and expose events for React components to subscribe to.

``
TODO: document the "createOple" function
`

$3

There are two ways to declare an Ople subclass.

Pick whichever you prefer!

#### createClass

Classes made by createClass meet the following criteria:

- extends the Ople class for event emitting and disposable effects
- requires the new keyword to be constructed
- can be extended

`ts
import {createClass, auto} from 'ople'

// Declare your props in TodoProps
interface TodoProps {
content: string
}

// Declare your state and methods in TodoState
interface TodoState {
id: string
done: boolean
content: string
}

// Declare your events in TodoEvents
interface TodoEvents {
complete(): void
}

let nextId = 1

export const Todo = createClass(
'Todo',
props => (todo, set, emit) => {
set(props)
set({
id: nextId++,
done: false,
})
auto(() =>
todo.done && emit('complete')
)
}
)

// The type for Todo is declared like so:
import {ReadonlyOpleObject} from 'ople'
export interface Todo extends ReadonlyOpleObject {}
`

#### extends Ople

The Ople class can be extended by any class. This makes your class compatible with
Ople mixins, and it can even emit its own events.

The initOple function lets your class create reactions and event listeners with
automatic disposal. If you create an Ople object inside initOple's callback,
it will be attached to the Ople context, which means the attached Ople object will
have its dispose method called when the Ople context is disposed.

`ts
import {Ople, initOple, auto} from 'ople'

// Declare your props in TodoProps
interface TodoProps {
content: string
}

// Declare your events in TodoEvents
interface TodoEvents {
complete(): void
}

let nextId = 1

class Todo extends Ople {
id = nextId++
done = false
content!: string // The ! is required to avoid this.content = props.content syntax

constructor(props: TodoProps) {
super()

// // This line is not needed, because of our set(props) call
// this.content = props.content

// Use the initOple function to set the Ople context, which
// handles the disposal of any listeners or reactions created
// inside the callback.
initOple(this, (self, set, emit) => {
// Merge the props object into this
set(props)

// Create a reactive callback
auto(() => self.done && emit('complete'))

// Attach listeners to self (or any other Ople object)
self.on({
complete() {
console.log('Todo completed:', self)
},
})
})
}

toggleDone() {
this.done = !this.done
}
}

const todo = new Todo({ content: 'Hello world' })

// BAD: Ople objects are readonly outside their initializer.
todo.done = true

// GOOD: Exposing a method is best practice.
todo.toggleDone()
`

Mixins

Mixins are functions that attach state, event listeners, and reactions to the
Ople context in which they are called. Any function can be a mixin, just like
any function can be a React hook.

`js
export function mixin() {
// TODO: mixin example
}

const state = createOple(() => {
mixin()
})
`

Ople also provides a few mixin helpers.

$3

The setEffect function lets you attach a disposable object to the current
Ople context, so the former is disposed of when the latter is, but not vice
versa.

You must provide an "owner" object as a cache key, in case you need the effect
disposed of before the Ople context is disposed.

`ts
import {setEffect} from 'ople'

function subscribe(source, effect) {
let subscriber
setEffect(source, active => {
if (active) {
subscriber = source.subscribe(effect)
} else {
subscriber.dispose()
}
})
}
`

Then, inside an Ople context, we can use our subscribe mixin.

`ts
// The source can be any object from your favorite library,
// assuming it has a subscribe method that returns a disposable.
const source = {}

const state = createOple((self, set, emit) => {
subscribe(source, value => {
console.log('Source changed:', value)
})
})
`

$3

The setState function is made for mixins that need to update state
by merging patch objects.

`ts
import {setState} from 'ople'

function makeUndoable() {
// Expose state and/or methods
setState({
history: [],
undo() {...},
redo() {...},
})
}
`

$3

These functions are for accessing the current Ople context. Use getOple
if you want to check for null manually. Otherwise, use expectOple to
throw an error when no Ople context is active.

`ts
import {expectOple} from 'ople'

interface MixinState {
foo: number
}

interface MixinEvents {
bar(): void
}

function mixin() {
const self = expectOple()
self.set({ foo: 0 })
self.on('bar', () => {
console.log('bar!')
})
}
``