React Decoupler

Note

The original project is available at https://www.npmjs.com/package/react-decoupler, and is the work of Tommy Groshong. Unfortunately, the package hasn't been updated in a long time and the github repository has been archived by the owner. I still need to use this in some legacy projects that I am working on, and so I have done a very simple update to the dependencies and configuration to allow it to be used with React 18. The existing tests are all running and passing and things seem to be working. I make no garuantees that this is a stable or reliable upgrade however.

Overview

React Decoupler is a simple dependency injection / service locator utility designed to help you decouple your React components from outside concerns and make it easier to reuse, refactor, and test your code.

Installation

• NPM: npm install --save react-decoupler
• Yarn: yarn add react-decoupler

Explanation

How simple is it? RIDICULOUSLY SIMPLE! No Really. It's just a simple data structure passed down via React Context that maps "service keys" to "services", all wrapped in an ergonomic API with a bunch of helpful react-specific hooks and components to make accessing it easier.

Why would you use this? Because you are busy, and this saves you the effort of writing the few hundred lines of code, glue, and tests to provide the same behavior and helpful API.

Examples

Simple Example

import React from 'react';
import ReactDOM from 'react-dom';
import { DecouplerProvider, useServices } from 'react-decoupler';

const serviceMap = {
  helloworld: name => `Hello, ${name ? name : 'World'}!`,
};

function App() {
  const [getGreeting] = useServices(['helloWorld']);
  return (
    <div>
      <span>{getGreeting()}</span>
      <span>{getGreeting('Foo')}</span>
    </div>
  );
}

ReactDOM.render(
  <DecouplerProvider services={serviceMap}>
    <App />
  </DecouplerProvider>,
  document.getElementById('app')
);

Alternate Example

import React from 'react';
import ReactDOM from 'react-dom';
import {
  DecouplerProvider,
  ServiceLocator,
  useServices,
} from 'react-decoupler';
import apiClient from './myApiClient';

const locator = new ServiceLocator();
locator.register('apiClient', apiClient);

function App() {
  const [apiClient] = useServices(['apiClient']);
  const [loading, setLoading] = React.useState(false);
  const [data, setData] = React.useState([]);

  React.useEffect(() => {
    apiClient
      .loadData()
      .then(setData)
      .finally(() => setLoading(false));
  }, [apiClient]);

  if (loading) {
    return <div>Loading...</div>;
  }

  return <div>{/* do stuff with data*/}</div>;
}

ReactDOM.render(
  <DecouplerProvider locator={locator}>
    <App />
  </DecouplerProvider>,
  document.getElementById('app')
);

Big Example

See example/ directory.

API Reference

ServiceLocator

A JavaScript Class that implements service registration and resolution.

Public Methods

class ServiceLocator
  static fromServices(services)
  register(key, service, options)
  resolve(dependencies)
  clearDependencyCache()

• static fromServices(services: {}): Factory function to create a ServiceLocator instance filled with the services from the provided vanilla JS object. Each key-value entry of the service object becomes a registered service in the locator.

• register(key, service, options = {}): Register a single service with a given key. Any value may be used as a key or a service. Supported options:

  • allowOverwrite: Boolean: When true, will replace any existing service registration using the same key. An error is thrown if a key is already registered and then a client attempts to re-register without this option.

  • withParams: Array<any>: Binds the given array of parameters as arguments to the service (value of the service must be a callable that supports .bind()). The binding happens at first-resolve-time and is consistent between calls. Use in conjunction with the Lookup function if you want to bind to services in the Injector. Defaults to undefined.

  • asInstance: boolean: When true, the locator will call new on the service value when resolving it. Will return a new instance every call. Defaults to false.

• resolve(dependencies: {} | []): Accepts an array or object of service keys and returns a matching collection of resolved services.

  • When using an array of service keys, the order of the returned services will match with the keys.
  • When using an object of service keys, the name mapping is {'name': 'ServiceKey'}.

• clearDependencyCache(): Clears the resolution cache of all parameter bound services. When is this useful? If you are dynamically registering services (e.g. calling locator.register() inside a component or function) and want to force all future resolutions to forget the previous value of that registered service key, call this method to delete the previously cached services. The drawback to calling this function is that it forces certain service functions/classes to resolve as new object references (i.e. useEffect and useMemo that were relying on consistent reference in some consumers will misbehave) so you need to be careful when you call it.

Usage

class A {}
class B {}

function cHelper(num, str) {
  return str + num;
}

class D {
  constructor(KlassA, instanceB, num) {
    this.instanceA = new KlassA();
    this.instanceB = instanceB;
    this.num = num;
  }
}

const locator = new ServiceLocator();

locator.register('A', A);
locator.register('B', B, { asInstance: true });
locator.register('C', cHelper, { withParams: [123, 'Hi: '] });
locator.register('D', D, {
  asInstance: true,
  withParams: [Lookup('A'), Lookup('B'), 123],
});

// Option 1: Array resolve

const [KlassA, b, instanceC, d] = locator.resolve(['A', 'B', 'C', 'D']);

// Option 2: Object resolve (equivalent)

const { KlassA, b, instanceC, d } = locator.resolve({
  KlassA: 'A',
  b: 'B',
  instanceC: 'C',
  d: 'D',
});

Lookup()

Utility used in conjunction with the ServiceLocator.register option {withParams: []} to indicate to the ServiceLocator it should look for a service with that key during resolution.

Usage

function foo(bar, iBar) {
  console.assert(bar === 'Bar');
  console.assert(iBar instanceof Bar);
}

class Bar {}

// In "withParams", 'Bar' will be a string bound to first argument of foo and
// Lookup('Bar') will be an instance of Bar class bound to the second argument

locator.register('Foo', foo, { withParams: ['Bar', Lookup('Bar')] });

locator.register('Bar', Bar, { isInstance: true });

const [resolvedFoo] = locator.resolve(['Foo']);
resolvedFoo();

DecouplerProvider

React Context Provider. Wrap your components with this provider to enable the rest of the helper functions and components.

Supported Props

Supply one of the following props, but not both:

• locator: an instance of ServiceLocator (or API compatible object)
• services: Vanilla JS object mapping service key names to services. e.g. {ServiceKey: class MyService {}}

Usage

class MyService {};

const locatorInstance = new ServiceLocator();

locatorInstance.register('ServiceKey', MyService);

function App() {
  return (
    <DecouplerProvider locator={locatorInstance}>
      <YourApp />
    </DecouplerProvider
  )
}

Or with a "Services" mapping object.

class MyService {};

const servicesMap = {
  'ServiceKey': MyService
};

function App() {
  return (
    <DecouplerProvider services={servicesMap}>
      <YourApp />
    </DecouplerProvider
  )
}

useLocator()

Hook to return the internal ServiceLocator instance from context.

Usage

function App() {
  const locator = useLocator();
  const [A] = locator.resolve(['A']);
  return <div />;
}

useServices()

Hook to resolve and return the given dependencies.

Usage

const SERVICES = ['A', 'B'];

const ALT_SERVICES = { a: 'A', b: 'B' };

function App() {
  const [A, B] = useServices(SERVICES);
  const { a, b } = useServices(ALT_SERVICES);

  return <div />;
}

LocateServices

React Component for locating services and passing to a children render prop.

Usage

function App() {
  return (
    <LocateServices deps={['funcKey', 'ServiceClass', 'val']}>
      {([func, ServiceClas, val]) => {
        return <div />;
      }}
    </LocateServices>
  );
}

withServices()

Higher-order Component for injecting services as props.

Usage

// Array service resolution keys:
function AppServiceArray({ services }) {
  const [serviceA, serviceB] = services;
  return <div />;
}

AppServiceArray.dependencies = ['AServiceKey', 'BServiceKey'];
export const WrappedAppServiceArray = withServices(AppServiceArray);

// Object service resolution keys:
function AppServiceObj({ serviceA, serviceB }) {
  return <div />;
}

AppServiceObj.dependencies = {
  serviceA: 'AServiceKey',
  serviceB: 'BServiceKey',
};

export const WrappedAppServiceObj = withServices(AppServiceObj);

Contributing

Development of React Decoupler happens in the open on GitHub, and we are grateful to the community for contributing bugfixes and improvements. Read below to learn how you can take part in improving React Decoupler.

TODO: contributing help

Code of Conduct

This project follows Test Double's code of conduct for all community interactions, including (but not limited to) one-on-one communications, public posts/comments, code reviews, pull requests, and GitHub issues. If violations occur, Test Double will take any action they deem appropriate for the infraction, up to and including blocking a user from the organization's repositories.

License

React Decoupler is MIT licensed.