Readme

Optice

Like redux, but no reducers, no actions

Usage

npm install optice

import { L, createStore } from 'optice'

const initialState = {
  user: {
    name: '',
    email: '',
  },
  company: {
    name: '',
    okato: 0,
  }
}

const store = createStore(initialState)

const userLens = L.prop('user')
const companyLens = L.prop('company')

const nameLens = L.prop('name')
const emailLens = L.create(
  (state) => state.email,
  (email) => (state) => ({ ...state, email }),
)
// same as `L.prop('email')`

const userNameLens = L.compose(userLens, nameLens)
const companyNameLens = L.compose(companyLens, nameLens)

const fetchUser = async () => ({ name: 'Foo Bar', email: '[email protected]' })

const loadUser = () => async ({ updateState }) => {
  updateState(userLens, await fetchUser())
}

In console should be this output:

BEFORE { name: '', email: '' } { name: '', okato: 0 }
UPDATE { name: 'Foo Bar', email: '[email protected]' } { name: '', okato: 0 }
UPDATE { name: 'Foo Bar', email: '[email protected]' } { name: 'Company', okato: 0 }

API

createStore

createStore(initialState): Store

Create new store object.

Store.execute

store.execute(command: Function, ...args: any[]): result

Run command function with store methods ({ updateState, readState, execute }) and passed arguments. Immediatly return result of command.

const command = (a, b) => ({ updateState, readState, execute }) => {
  // read, update state
  // or execute another command
  return 1 + a + b
}

store.execute(command, 2, 1) === 4

Store.getState

store.getState(): State

Just return current state

Store.readState

store.readState(lens: Lens): Value

Read value from state through lens.

const lens = L.prop('data')

const initialState = {
  data: 1
}

const store = createStore(initialState)
const value = store.readState(lens)

console.assert(value === 1)

Store.setState

store.setState(newState: State): void

It notify all subscribers. Replace state, returns nothing.

const initial = { a: 1, b: 2 }

const store = createStore(initial)

store.subscribe(state => {
  console.log('updated')
  console.assert(state.a === 5)
})
store.setState({ a: 5, b: 10 })

Store.subscribe

store.subscribe(listener: Function): Function

Add listener to subscribers list, returns unsubscribe function.

const store = createStore({ a: 1 })

const unsubscribe = store.subscribe(state => {
  console.log('update', state)
})

store.setState({ a: 2 }) // > update { a: 2 }

unsubscribe()
store.setState({ a: 3 }) // nothing

Store.updateState

store.updateState(lens: Lens, valueOrFunc: any | Function): void

It notify all subscribers. Update piece of state through lens. If function passed update state with L.over, else use L.write to just set value.

const lens = L.prop('a')

const store = createStore({ a: 1 })

store.updateState(lens, 2)
console.assert(store.getState().a === 2)

store.updateState(lens, value => value + 1)
console.assert(store.getState().a === 3)

L.create

L.create(getter: Function, setter: Function): Lens

Create new lens.

Getter is just function that received state. Should return piece of state.

Setter is function that received passed value, return function that received state. Should return new version of passed state.

Getter and Setter should be pure functions.

const lens = L.create(
  state => state.value,
  value => state => ({ ...state, value }),
)

L.view

L.view(state: State, lens: Lens): any

Read value from state through lens.

const lens = L.create(
  state => state.value,
  value => state => ({ ...state, value }),
)

const state = { value: 'foo' }
const value = view(state, lens)

console.assert(value === 'foo')

L.write

L.write(state: State, lens: Lens, value: any): State

Immutable update piece of state through lens. Return new version of state.

const state = { foo: { bar: 1 } }

const fooLens = L.prop('foo')
const barLens = L.prop('bar')
const fooBarLens = L.compose(fooLens, barLens)

const newState = L.write(state, fooBarLens, 2)
console.assert(newState.foo.bar === 2)

L.over

L.over(state: State, lens: Lens, fn: (value) => value): State

Like L.write but use function to update value. Return new version of state.

const state = { foo: 100 }

const fooLens = L.prop('foo')
const updater = (value) => value + value

const newState = L.over(state, fooLens, updater)
console.assert(L.view(state, fooLens) === 200)

L.compose

L.compose(...lenses: Lens[]): Lens

L.compose can be used only for this lenses

Perform lens composition. Returns one lens.

If passed no lens, returns empty lens L.create(s => s, v => s => s).

If passed one lens, returns its.

const a = L.create(
  state => state.a,
  value => state => ({ ...state, a: value })
)

const b = L.create(
  state => state.b,
  value => state => ({ ...state, b: value })
)

const ab = L.compose(a, b)

// same as

const ab2 = L.create(
  state => state.a.b,
  value => state => ({ ...state, a: { ...state.a, b: value } }),
)

L.prop

L.prop(name: string): Lens

Makes lens to read/write property.

const fooLens = L.prop('foo')
// Same as
const fooLens2 = L.create(
  state => state.foo,
  value => state => ({ ...state, value: foo })
)