kelabang / nativebridge

Lightweight and efficient bridge between webview and native app

@nrk/nativebridge

Native Bridge is a lightweight and efficient bridge between webview and native app. It's primary use case is to share state between native apps and javascript in webviews.

• Browser documentation
• Android documentation
• iOS documentation
• How does it work

Support

Tested on Android 4.4.4+	iOS 10.2+

---

Browser

Used as a producer/consumer-interface for passing messages to/from native app (iOs/Android). Following an EventEmitter interface (on/once/off/emit). In addition an RPC-interface makes calling native methods a breeze.

EMIT - send to native:

nativebridge.emit('test', { foo: 'bar' })  // Emit 'test' event with data (must be object) to native

ON/ONCE - receives from native:

nativebridge.on('test', (data) => {})       // Bind handler to 'test' event emitted from native
nativebridge.once('test', (data) => {})     // Bind handler to 'test' (one time only) event emitted from native

OFF: - remove handler(s)

nativebridge.off('test')                    // Unbind all handlers for 'test' event
nativebridge.off('test', (data) => {})      // Unbind specific handler for 'test' event

RPC: - make call to native app using topic as contract

Make a remote procedure call (RPC) using nativebridge interfaces as described above. Resolves with data on completion, or rejects with error details from the app (or timeout).

// Auto-bind handlers (once/emit) to complete an RPC-call to native
nativeBridge.rpc({                          
  topic: 'test',                             // using 'test' as event
  data: {},                                 // with data (args)
  resolve: (data) => {},                    // using callback on success
  reject: (err) => {},                      // or rejection on error
  timeout: 1000                             // with a timeout threshold
})

Installation

USE WITH NPM:

npm install @nrk/nativebridge

const nativebridge = require('@nrk/nativebridge')

USE WITH SCRIPT TAG:

<script src="https://static.nrk.no/nativebridge/X.X.X/nativebridge.min.js"></script>
<!-- window.nativebridge is now defined -->

USE WITH REQUIRE.JS:

require(['https://static.nrk.no/nativebridge/X.X.X/nativebridge.min.js'], function(nativebridge) {
  /* code here */
});

---

How does it work

Emit

A data object is sent using topic as topic to an exposed method on either:

• iOS:

window.webkit.messageHandlers.nativebridgeiOS.postMessage({topic: "test", data: {foo: "bar"}})

• Android:

window.NativeBridgeAndroid.send(JSON.stringify({topic: "test", data: {foo: "bar"}}))

Android/iOS handler

Topic-handlers are mapped to native functions, using data-object as an argument e.g topicHandler({topic: "test", data: {foo: "bar"}}). The app injects a js-snippet to dispatch a message back to the webpage using CustomEvents:

window.dispatchEvent(new CustomEvent('nativebridge', { detail: {topic, data} }))

On

The CustomEvent dispatched from the native app is ran using attached callback-handlers on the given topic.

Error handling

If an error occurs in the native app, an Error object will be rejected, eg.

err.message = '[{message: "no handler available", errorCode: 100}]'

RPC

The RPC-method is made to simplify on/off/emit-logistics. In addition it supports a timeout, which will throw an error if timeout is reached:

err.message = 'RPC for test using {} timed out after 1000ms'

---

Local development (web)

First clone @nrk/nativebridge and install its dependencies:

git clone [email protected]:nrkno/nativebridge.git
cd nativebridge
npm install && npm start

Building and committing

After having applied changes, remember to build before pushing the changes upstream.

git checkout -b feature/my-changes
# update the source code
npm run build
git commit -am "Add my changes"
git push origin feature/my-changes
# then make a PR to the master branch,
# and assign another developer to review your code

NOTE! Please also make sure to keep commits small and clean (that the commit message actually refers to the updated files).
Stylistically, make sure the commit message is Capitalized and starts with a verb in the present tense (for example Add minification support).