davidkpiano

import React from 'react';

import * as My from './components/my-components.js';

export default class App extends React.Component {
  render() {
    return (
      <div>
        <My.Foo />
        <My.Bar />

davidkpiano

As the number of different possible states and transitions between states in a user interface grows, managing styles and animations can quickly become complicated. Even a simple login form has many different "user flows":

https://codepen.io/davidkpiano/pen/WKvPBP

State machines are an excellent pattern for managing state transitions in user interfaces in an intuitive, declarative way. We've been using them a lot on the Keyframers as a way to simplify otherwise complex animations and user flows, like the one above.

So, what is a state machine? Sounds technical, right? It’s actually more simple and intuitive than you might think. (Don’t look at Wikipedia just yet… trust me.)

Let’s approach this from an animation perspective. Suppose you’re creating a loading animation, which can be in only one of four states at any given time:

davidkpiano

const updatePosition = assign({
  position: (_, event) => event.position,
})

function geoService(context, event) {
  return cb => {
    if (!navigator.geolocation) {
      cb({
        type: 'error',
        error: new Error('Geolocation is not supported'),

davidkpiano

Machine({
  initial: 'idle',
  context: {
    // the position of the box
    x: 0,
    y: 0,
    // where you clicked
    pointerx: 0,
    pointery: 0,
    // how far from where you clicked

davidkpiano

const machine = Machine({
  initial: "start",
  context: {
    selected: [],
    x1: 0,
    y1: 0,
    x2: 0,
    y2: 0,
    drag: {
      x1: 0,

davidkpiano

// ----
// Sass (v3.4.11)
// Compass (v1.0.3)
// ----


@function math-pow($number, $exp) {
    @if (round($exp) != $exp) {
      @return math-exp($exp * math-ln($number));
    }

davidkpiano

function Example() {
  const [{ isLoading, error, data }] = useMachine(
    createQuery('repoData', () => fetch('...').then((res) => res.json()))
  );
}

davidkpiano

import {
  useReducerWithEffects,
  // hand-wavey, but meant to be used by React to create something
  // external will produce async values sent to components
  createEffect 
} from 'react';

function fetchUserEffect(id, parentRef) {
  const controller = new AbortController();
  const signal = controller.signal;

davidkpiano

const machine = Machine({
  id: 'ATM',
  initial: 'idle',
  states: {
    idle: {
      on: {
        INSERT_CARD: 'authenticating',
      }
    },
    authenticating: {

davidkpiano

// ----
// Sass (v3.4.12)
// Compass (v1.0.3)
// ----

$scotch-color-key: 'base' !default;

$scotch-colors: (
  'primary': (
    'base': #8e3329,