kea

A kea is two things:

1. An extremely smart mountain parrot from New Zealand.
2. An equally smart architecture for frontend webapps, built on top of React and Redux.

Try it out

Open the documentation (AKA demo app) and view its source on GitHub.

In the documentation you will find several examples with source. Check it out!

The basics

You create and connect kea logic stores to your components like this:

import { kea } from 'kea'

@kea({
  key: (props) => props.id,
  path: (key) => ['scenes', 'homepage', 'slider', key],

  actions: () => ({
    updateSlide: index => ({ index })
  }),

  reducers: ({ actions, key, props }) => ({
    currentSlide: [props.initialSlide || 0, PropTypes.number, {
      [actions.updateSlide]: (state, payload) => payload.key === key ? payload.index % images.length : state
    }]
  }),

  selectors: ({ selectors }) => ({
    currentImage: [
      () => [selectors.currentSlide],
      (currentSlide) => images[currentSlide],
      PropTypes.object
    ]
  })
})
export default class Slider extends Component {
  render () {
    const { currentSlide, currentImage } = this.props
    const { updateSlide } = this.actions

    const title = `Image copyright by ${currentImage.author}`

    return (
      <div className='kea-slider'>
        <img src={currentImage.src} alt={title} title={title} />
        <div className='buttons'>
          {range(images.length).map(i => (
            <span key={i} className={i === currentSlide ? 'selected' : ''} onClick={() => updateSlide(i)} />
          ))}
        </div>
      </div>
    )
  }
}

Inline kea also supports Sagas. They will be started and terminated together with your component! Each instance of your component runs its own sagas!

import { kea } from 'kea'

@kea({
  key: (props) => props.id,

  path: (key) => ['scenes', 'homepage', 'slider', key],

  actions: () => ({
    updateSlide: index => ({ index })
  }),

  reducers: ({ actions, key, props }) => ({
    currentSlide: [props.initialSlide || 0, PropTypes.number, {
      [actions.updateSlide]: (state, payload) => payload.key === key ? payload.index % images.length : state
    }]
  }),

  selectors: ({ selectors }) => ({
    currentImage: [
      () => [selectors.currentSlide],
      (currentSlide) => images[currentSlide],
      PropTypes.object
    ]
  }),

  start: function * () {
    const { updateSlide } = this.actions

    console.log('Starting homepage slider saga')
    // console.log(this, this.actions, this.props)

    while (true) {
      const { timeout } = yield race({
        change: take(action => action.type === updateSlide.toString() && action.payload.key === this.key),
        timeout: delay(5000)
      })

      if (timeout) {
        const currentSlide = yield this.get('currentSlide')
        yield put(updateSlide(currentSlide + 1))
      }
    }
  },

  stop: function * () {
    console.log('Stopping homepage slider saga')
  },

  takeEvery: ({ actions, workers }) => ({
    [actions.updateSlide]: workers.updateSlide
  }),

  workers: {
    updateSlide: function * (action) {
      if (action.payload.key === this.key) {
        console.log('slide update triggered', action.payload.key, this.key, this.props.id)
        // console.log(action, this)
      }
    }
  }

  // Also implemented:
  // takeLatest: () => ({}),
  // sagas: [ array of sagas from elsewhere that run with the component ],
})
export default class Slider extends Component {
  render () {
    const { currentSlide, currentImage } = this.props
    const { updateSlide } = this.actions

    const title = `Image copyright by ${currentImage.author}`

    return (
      <div className='kea-slider'>
        <img src={currentImage.src} alt={title} title={title} />
        <div className='buttons'>
          {range(images.length).map(i => (
            <span key={i} className={i === currentSlide ? 'selected' : ''} onClick={() => updateSlide(i)} />
          ))}
        </div>
      </div>
    )
  }
}

When the logic grows too big, you may extract it from your components and give it a new home in logic.js files.

// logic.js
export default kea({
  path: () => ['scenes', 'homepage', 'index'],
  actions: ({ constants }) => ({
    updateName: name => ({ name })
  })
  // ...
})

// index.js
import sceneLogic from './logic'

@sceneLogic
export default class HomepageScene extends Component {
  render () {
    const { name } = this.props
    const { updateName } = this.actions

    // ...
  }
}

If you only wish to import some properties and actions from your logic stores, use the @connect decorator or add connect: { props: [], actions: [] } inside @kea({}), like so:

// index.js
import sceneLogic from './logic'
import sceneSaga from './saga'

@connect({
  actions: [
    sceneLogic, [
      'updateName'
    ]
  ],
  props: [
    sceneLogic, [
      'name',
      'capitalizedName'
    ]
  ],
  sagas: [
    sceneSaga
  ]
})
export default class HomepageScene extends Component {
  render () {
    const { name } = this.props
    const { updateName } = this.actions

    // ...
  }
}

Connecting to your app

Starting with 0.19, all you need to do is to hook up redux and redux-saga as you normally would, and then just add keaReducer and keaSaga, like this:

import { keaSaga, keaReducer } from 'kea' // add this

const reducers = combineReducers({
  routing: routerReducer,
  scenes: keaReducer('scenes') // add this
})

const sagaMiddleware = createSagaMiddleware()
const finalCreateStore = compose(
  applyMiddleware(sagaMiddleware),
  applyMiddleware(routerMiddleware(browserHistory))
)(createStore)

const store = finalCreateStore(reducers)

sagaMiddleware.run(keaSaga) // add this

Singleton and dynamic logic stores

If you specify the key key in kea({}), kea will create a dynamic logic store. Each component you connect it to, will have its own actions and reducers.

Omitting this key key will create singletons. You can then export these singletons and connect to them as described above.

Redux all the way!

When you run kea({}), you get in return an object that exposes all the standard redux constructs.

// homepage/logic.js
export default kea({ ... })

// homepage/index.js
import homepageLogic from '~/scenes/homepage/logic'

homepageLogic.path === ['scenes', 'homepage', 'index']
homepageLogic.selector === (state) => state.scenes.homepage.index

homepageLogic.actions === { updateName: (name) => { ... }, increaseAge: (amount) => { ... }, ... }
homepageLogic.reducer === function (state, action) { ... }
homepageLogic.selectors === { name: (state) => state.scenes.homepage.index.name, capitalizedName: ... }

Sagas

Inline this inside kea({}) or use the separate createSaga({}) helper to create sagas:

import { createSaga } from 'kea'

import sceneLogic from '~/scenes/homepage/logic'
import sliderLogic from '~/scenes/homepage/slider/logic'

export default createSaga({
  // pull in actions from logic stores
  actions: () => ([
    sceneLogic, [
      'updateName',
      'increaseAge',
      'decreaseAge'
    ],
    sliderLogic, [
      'updateSlide'
    ]
  ]),

  // bind some actions to worker functions
  takeEvery: ({ actions }) => ({
    [actions.updateName]: this.nameLogger,
    [actions.increaseAge]: this.ageLogger,
    [actions.decreaseAge]: this.ageLogger
  }),
  // also available: takeLatest

  // main loop of saga
  // - update the slide every 5 sec
  start: function * () {
    // to ease readability we always list the actions we use on top
    const { updateSlide } = this.actions

    while (true) {
      // wait for someone to call the updateSlide action or for 5 seconds to pass
      const { timeout } = yield race({
        change: take(updateSlide),
        timeout: delay(5000)
      })

      // if timed out, advance the slide
      if (timeout) {
        // you can the contents of a logic store instance via "yield logic.get('property')"
        const currentSlide = yield sliderLogic.get('currentSlide')
        // dispatch the updateSlide action
        yield put(updateSlide(currentSlide + 1))
      }

      // re-run loop - wait again for 5 sec
    }
  },

  // clean up if needed
  stop: function * () {
    console.log('Closing saga')
  },

  // on every updateName
  nameLogger: function * (action) {
    const { name } = action.payload
    console.log(`The name changed to: ${name}!`)
  },

  // on every increaseAge, decreaseAge
  ageLogger: function * (action) {
    const age = yield sceneLogic.get('age')
    console.log(`The age changed to: ${age}!`)
  }
})

Read the documentation for redux-saga/

Scenes

You can use all the logic store reducers and sagas individually in your existing application.

If, however, you favor convenience, you may combine them into scenes.

Scenes are defined in scene.js files like so:

// scenes/homepage/scene.js
import { createScene } from 'kea/scene'

import sceneComponent from '~/scenes/homepage/index'
import sceneSaga from '~/scenes/homepage/saga'

import sliderSaga from '~/scenes/homepage/slider/saga'

export default createScene({
  name: 'homepage',
  component: sceneComponent,
  sagas: [
    sceneSaga,
    sliderSaga
  ]
})

You may then access the combined scene like so:

import homepageScene from '~/scenes/homepage'

homepageScene.saga === function * () { ... }                    // start the scene sagas in parallel

or plug it into the kea-logic routing helpers.

Routing

Give redux-router a helping hand:

// routes.js
import { combineScenesAndRoutes } from 'kea/scene'

const scenes = {
  homepage: require('bundle?lazy&name=homepage!./homepage/scene.js'),
  todos: require('bundle?lazy&name=todos!./todos/scene.js')
}

const routes = {
  '/': 'homepage',
  '/todos': 'todos',
  '/todos/:visible': 'todos'
}

export default combineScenesAndRoutes(scenes, routes)

... and have those scenes lazily loaded when route is accessed.

Code structure

While logic stores can exist anywhere, it is highly recommended to organise your code like this:

• scenes - a scene is a page or a subsystem in your app
• components - react components that are shared between scenes
• utils - javascript utils shared between scenes

Side note: as we strive for simplicity, readability and clarity, we will use JavaScript Standard Style and skip semicolons. They are added/removed as needed in the transpiling/minimising stage, and add no value. Any "I forgot the semicolon" errors you might be worried about will be caught by the linter anyway. (Please install eslint and plugins for your IDE!)

Here's a typical structure:

scenes/homepage/
- index.js    # the react component
- logic.js    # actions, reducers, selectors
- saga.js     # saga
- styles.scss # styles for this scene
- scene.js    # one of these per scene

scenes/homepage/slider/
- _assets/    # some images
- index.js    # the react component
- logic.js    # actions, reducers, selectors
- saga.js     # saga
- styles.scss # styles for the slider

scenes/todos/
- index.js    # the react component
- logic.js    # actions, reducers, selectors
- saga.js     # saga
- styles.scss # styles for this scene
- scene.js    # one of these per scene

scenes/todos/todo/
- index.js    # the react component

components/
- header/
  - index.js
  - styles.scss

utils/
- create-uuid.js
- range.js
- delay.js

scenes/
- index.js
- routes.js
- styles.scss

/
- index.html
- index.js
- store.js

Scaffolding

Open the demo app and browse its code.

To run the same example app on your machine, just type these commands:

npm install kea -g
kea new my-project
cd my-project
npm install # or yarn
npm start

and open http://localhost:2000/.

Later inside my-project run these to hack away:

kea g scene-name                               # new scene
kea g scene-name/component-name                # component under the scene
kea g scene-name/component-name/really-nested  # deeply nested logic

More documentation coming soon! Please help if you can!