Ditto is bringing web support to its Flutter SDK so Flutter applications can be deployed to the web with minimal changes. This guide shows you how to get started when porting an application for the web and explains limitations.

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Public Preview

Support for the web platform is currently in public preview. Not all features are available and some APIs may change in the final release. Available APIs include:
  • Querying and observing documents in the Ditto store
  • Sync with the Ditto cloud using sync subscriptions
  • Managing transport configuration, starting and stopping sync
  • Online with authentication and online playground identities.
  • Configuring the Ditto Logger
Coming soon:
  • Attachments
  • Connection handling using connection request handlers
  • Closing the Ditto instance
  • Presence
  • Small Peer info

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Getting Started

To use the public preview, add the ditto_live package to your pubspec.yaml file with the version 4.9.1-web-preview.0: 
dependencies:
  ditto_live: 4.9.1-web-preview.0
Ditto’s Flutter Quick Start app is a good starting point for trying out Ditto on the web with an existing app. Follow the Flutter Install Guide guide to get familiar with the basics of using Ditto in a Flutter app. For adding web support to your existing Flutter app, refer to the instructions in the official Flutter documentation. Ditto doesn’t require any additional setup. However, some APIs have minor differences as described below. For production use it is strongly recommended to use compression for serving web assets.

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Web Assets

When Ditto is used on the web, it needs to download and initialize assets for its WebAssembly binary. This happens automatically when calling await Ditto.init(). By default, assets are bundled with the application and loaded from the same web server that serves the application. After running flutter build web, you can find those in the build/web/assets/packages/ditto_live/lib/assets directory. Alternatively, you can host the contents of that directory on a CDN or other web server and configure Ditto to load assets from there. All contents of the directory, excluding the ditto.wasm file itself, must be reachable at the URL given by the wasmShimUrl parameter. The ditto.wasm file can be served from a separate URL given by the wasmUrl parameter. Configuration for loading all assets from a CDN: 
await Ditto.init(
  wasmUrl: 'https://your-cdn.com/ditto-assets/ditto.wasm',
  wasmShimUrl: 'https://your-cdn.com/ditto-assets/',
);
Please consider your application’s loading UI while downloading the assets as it may take a few seconds to download and initialize the WebAssembly binary. It is strongly recommended to serve assets using a web server or CDN that supports compression. This will significantly reduce the download size of the assets and thereby the loading time of your application.

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Permissions

Make sure that your app does not attempt to request permissions that are not available on the web. Use Flutter’s built-in kIsWeb constant to conditionally request permissions only on mobile platforms. 
import 'package:flutter/foundation.dart';

if (!kIsWeb) {
  await [
    Permission.bluetoothConnect,
    Permission.bluetoothAdvertise,
    Permission.nearbyWifiDevices,
    Permission.bluetoothScan
  ].request();
}

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Peer-to-Peer Transports

On the web, Ditto only supports syncing with the Ditto cloud and does not directly connect to other devices. Make sure that your app only sets up peer-to-peer transports on mobile platforms.

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Considerations for Web

  • Flutter for Web is designed to work seamlessly with the Ditto cloud. Due to browser restrictions, direct peer-to-peer synchronization with other devices is not supported.
  • The web platform utilizes an in-memory Ditto store, meaning data is not retained across page reloads.
  • Ditto’s Flutter SDK currently supports the default build mode for the web.
  • When developing with Flutter’s development server, it is required to quit and restart the server after making changes to the source code of your app (support for hot restart is in development).