external_links

A package that provides abstraction to handle external links to your apps with an unified interface whether it's a push notification, a deep link, a dynamic link or whatever.

Components

The object that represents the link information. It consists of the following properties and getters:

  • title of the link, usually associated to the title of a push notification
  • content of the link, usually associated to the content of a push notification
  • args of the link, usually associated to the arguments of a push notification
  • uri of the link, usually associated to the uri of a deep link
  • authenticationRequired tells if is being logged in is required to process this link
  • getHandler returns the handler for the link. If no operation handler is needed, return an instance of EmptyHandler.
  • mapFactory is used to create links from a Map<String,dynamic>. Assign it as soon as possible
  • uriFactory is used to create links from an Uri. Assign it as soon as possible

Example:

class DummyLink extends ExternalLink {
  @override
  Map<String, dynamic> get args => {};

  @override
  bool get authenticationRequired => false;

  @override
  String get content => 'Dummy content! #${Random().nextInt(100000)}';

  @override
  ExternalLinkHandler getHandler([BuildContext context]) {
    if (context != null) {
      return DummyLinkHandler(context);
    } else {
      return EmptyHandler();
    }
  }

  @override
  String get title => 'Dummy title!';

  @override
  Uri get uri => null;
}

ExternalLinkHandler and ExternalLinkContextHandler

The handler of a link. This is used to perform actions when processing the link. Use ExternalLinkHandler if your actions do not need a BuildContext and if they do use ExternalLinkContextHandler instead.

Example:

class DummyLinkHandler extends ExternalLinkContextHandler {
  DummyLinkHandler(BuildContext context) : super(context);

  @override
  Future<void> processLinkWithContext(BuildContext context, ExternalLink link) {
    return showDialog(
      context: context,
      builder: (_) => AlertDialog(
        title: Text(link.title ?? ''),
        content: Text(link.content ?? ''),
      ),
    );
  }
}

ExternalLinksAdapter

The adapter that processes information into ExternalLinks, which will be automatically enqueued by the ExternalLinksBloc the adapter is passed to. It can be anything you need, for example you can use the following adapter if you're hooking your app to Firebase dynamic links:

class DynamicLinkAdapter extends ExternalLinksAdapter {
  StreamSubscription? _uriChangeSubscription;

  @override
  Future<void> init() async {
    try {
      final initialLink = await FirebaseDynamicLinks.instance.getInitialLink();

      final initialUri = initialLink?.link;

      if (initialUri != null) {
        _onUriLink(initialUri);
      }

      FirebaseDynamicLinks.instance.onLink(
        onSuccess: (linkData) async => _onUriLink(linkData?.link),
      );
    } on PlatformException catch (e, stackTrace) {
      //report error
    }
  }

  void _onUriLink(Uri? uri) {
    if (uri != null) {
      final link = ExternalLink.uriFactory(uri);
      emit(link);
    }
  }

  @override
  void dispose() {
    _uriChangeSubscription?.cancel();
    super.dispose();
  }
}

ExternalLinksBloc

The Bloc that manages the links queue.

Just instantiate it passing a list of ExternalLinksAdapter to its constructor. Note that you might need to call init on yout adapters in order to setting them up (usually useful when init containts async operations).

The Bloc takes in a ProcessLink event with the informations needed to process the current link of the queue and emits the following states:

  • ExternalLinksInitial: The initial state of the Bloc

  • ExternalLinkAvailable: Triggered whenever a new link is available on the queue

  • ExternalLinkProcessing: Triggered when a link is processing

  • NoExternalLinks: Triggered when the links queue is empty

Example:

BlocProvider<ExternalLinksBloc>(
    create: (_)=>ExternalLinksBloc(
        adapters: [
            DeepLinkAdapter()..init(), //an adapter for deep links
            CloudMessagingAdapter()..init(), //an adapter for push notifications
            //any other adapter
        ],
    ),
    child: //child here. Usually the MaterialApp
)

ExternalLinksListener

This is just a convenience class that listens to the ExternalLinks queue and processes them using their handler. It is optional to use this and you can listen directly to the ExternalLinksBloc instead and decide what to do upon receiving links.

The implementation is quite simple:

class ExternalLinksListener extends StatelessWidget {
  final Widget child;
  const ExternalLinksListener({
    Key? key,
    required this.child,
  }) : super(key: key);
  @override
  Widget build(BuildContext context) {
    return BlocListener<ExternalLinksBloc, ExternalLinksState>(
      listenWhen: (previous, current) => current is ExternalLinkAvailable,
      listener: (context, state) {
        if (state is ExternalLinkAvailable) {
          BlocProvider.of<ExternalLinksBloc>(context).add(
            ProcessLink(
              processFunction: (link) {
                return link.getHandler(context).processLink(link);
              },
            ),
          );
        }
      },
      child: child,
    );
  }
}

The ExternalLink class has two functions that can be assigned and used ad factory for the links:

  • mapFactory is used to create links from a Map<String,dynamic>
  • uriFactory is used to create links from an Uri

By default those are functions that return null. If you want to use them, just assign a new Function object to them.

These are totally optional since you are free to generate ExternalLinks in any way you like within an adapter, but they might be useful if you want somepalce centralized.

Considerations

This might look overkill ad first, but in my experience a solid architecture that allows to process external links to an app in a simple way can be a life saver on the long run.

Just set how many adapters you like to receive links information, just define how many link types you need. Despite the name Link you can actually use this as an inside notification system in your app too, or hooking an adapter to a websocket or whatever.

Suppose you're managing Deep links, and you currently manage two URLs. Whenever a new URL is needed, just define another link with its handler and update the factory function to return that too. Nothing else is needed.

I've used this architecture in a couple of projects (enterprise ones too) and it proved itself quite useful on the long run.

Libraries