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

Classes

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

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<TodoState, TodoEvents, [TodoProps]>(
  '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<TodoState, TodoEvents> {}

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.

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<TodoEvents> {
  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.

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

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

Ople also provides a few mixin helpers.

setEffect

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.

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.

// 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)
  })
})

setState

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

import {setState} from 'ople'

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

getOple and expectOple

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.

import {expectOple} from 'ople'

interface MixinState {
  foo: number
}

interface MixinEvents {
  bar(): void
}

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