@bem-react/di ·

Dependency Injection (DI) allows you to split React components into separate versions and comfortably switch them in the project whenever needed, e.g., to make a specific bundle.

DI package helps to solve similar tasks with minimum effort:

• decouple desktop and mobile versions of a component
• implement an experimental version of a component alongside the common one
• store components and their auxiliaries (like settings and functions) in a single place

Install

npm i -S @bem-react/di

Quick start

Note! This example uses @bem-react/classname package.

E.g., for a structure like this:

Components/
  Header/
    [e-mail]
    [e-mail]
  Footer/
    [e-mail]
    [e-mail]
App.tsx

First, create two files that define two versions of the App and use different sets of components: [e-mail] and [e-mail]. Put them near App.tsx.

In each App version ([e-mail] and [e-mail]) we should define which components should be used. Three steps to do this:

1. Create a registry with a particular id:

const registry = new Registry({ id: cnApp() })

2. Register all the needed components versions under a descriptive key (keys, describing similar components, should be the same across all the versions):

registry.set('Header', Header)
registry.set('Footer', Footer)

or

registry.fill({
  Header,
  Footer,
})

or

registry.fill({
  'id-1': Header,
  'id-2': Footer,
})

3. Export the App version with its registry of components:

export const AppNewVersion = withRegistry(registry)(AppCommon)

The files should look like this:

1. In App.tsx

import { cn } from '@bem-react/classname'

export const cnApp = cn('App')
export const registryId = cnApp()

2. In [e-mail]

import { Registry, withRegistry } from '@bem-react/di'
import { App as AppCommon, registryId } from './App'

import { Footer } from './Components/Footer/Footer@desktop'
import { Header } from './Components/Header/Header@desktop'

export const registry = new Registry({ id: registryId })

registry.set('Header', Header)
registry.set('Footer', Footer)

export const AppDesktop = withRegistry(registry)(AppCommon)

3. In [e-mail]

import { Registry, withRegistry } from '@bem-react/di'
import { App as AppCommon, registryId } from './App'

import { Footer } from './Components/Footer/Footer@mobile'
import { Header } from './Components/Header/Header@mobile'

export const registry = new Registry({ id: registryId })

registry.set('Header', Header)
registry.set('Footer', Footer)

export const AppMobile = withRegistry(registry)(AppCommon)

Time to use these versions in your app dynamically!

If in App.tsx your dependencies were static before

import React from 'react'
import { cn } from '@bem-react/classname'
import { Header } from './Components/Header/Header'
import { Footer } from './Components/Footer/Footer'

export const App = () => (
  <>
    <Header />
    <Footer />
  </>
)

Now the dependencies can be injected based on the currently used registry

with RegistryConsumer

import React from 'react'
import { cn } from '@bem-react/classname'
import { RegistryConsumer } from '@bem-react/di'

// No Header or Footer imports

const cnApp = cn('App')

export const App = () => (
  <RegistryConsumer id={cnApp()}>
    {({ Header, Footer }) => (
      <>
        <Header />
        <Footer />
      </>
    )}
  </RegistryConsumer>
)

with useRegistry (require react version 16.8.0+)

import React from 'react'
import { cn } from '@bem-react/classname'
import { useRegistry } from '@bem-react/di'

// No Header or Footer imports

const cnApp = cn('App')

export const App = () => {
  const { Header, Footer } = useRegistry(cnApp())

  return (
    <>
      <Header />
      <Footer />
    </>
  )
}

So you could use different versions of your app e.g. for conditional rendering on your server side or to create separate bundles

import { AppDesktop } from './path-to/App@desktop'
import { AppMobile } from './path-to/App@mobile'

Replacing components

Components inside registry can be replaced (e.g. for experiments) by wrapping withRegistry(...)(App) with another registry.

import { Registry, withRegistry } from '@bem-react/di'

import { AppDesktop, registryId } from './App@desktop'
import { HeaderExperimental } from './experiments/Components/Header/Header'

const expRegistry = new Registry({ id: registryId })

// replacing original Header with HeaderExperimental
expRegistry.set('Header', HeaderExperimental)

// AppDesktopExperimental will call App with HeaderExperimental as 'Header'
export const AppDesktopExperimental = withRegistry(expRegistry)(AppDesktop)

When App extracts components from registry DI actually takes all registries defined above and merges. By default higher defined registry overrides lower defined one.

If at some point you want to create registry that wan't be overrided just call the constructor with overridable: false.

const boldRegistry = new Registry({ id: cnApp(), overridable: false })

Extending components

You can extend (e.g. for experiments) a component using method extends(...) in overridden registry.

import { Registry, withRegistry, withBase } from '@bem-react/di'
import { AppDesktop, registryId } from './App@desktop'

const expRegistry = new Registry({ id: registryId })

// extends original Header
expRegistry.extends('Header', (BaseHeader) => (props) => (
  <div>
    <BaseHeader height={200} color={red} />
  </div>
))

// AppDesktopExperimental will call App with extended 'Header'
export const AppDesktopExperimental = withRegistry(expRegistry)(AppDesktop)

DI merges nested registries composing and ordinary components for you. So you always can get a reference to previous component's implementation.

Storing other

DI registry may keep not only components but also their settings and any other auxiliaries (like functions).

import { useRegistry } from '@bem-react/di'

const cnHeader = cn('Header')

export const Header = (props) => {
  const { theme, showNotification, prepareProps } = useRegistry(cnApp())

  // one function is used to fulfill props
  const { title, username } = prepareProps(props)

  useEffect(() => {
    // another function is used inside hook
    showNotification()
  })

  return (
    <header className={cnHeader({ theme })}>
      <h1>{title}</h1>
      <h2>Greetings ${username}</h2>
    </header>
  )
}