如何使用 Riverpod 包从 Flutter 中的 firebase 集合中获取所有文档？

Question

I am using the provider package and have a provider that gets its initial value from a global variable idea which a list of json data and is of type List<Map<String, dynamic>>.

following is the code for that, which is working expected.

final ideasListProvider = StateNotifierProvider<IdeaList>((ref) {
  return IdeaList([for (var i in ideas) Idea.fromJson(i)]);
});

Now what I am trying to achieve is replace the variable idea and instead use the list of documents I get from a collection I have on firebase.

But I am not sure how to proceed from here onwards.

Here's a second provider that fetches the snapshot form firestore.

final firbaseIdeaProvider = StreamProvider.autoDispose((ref) {
  return FirebaseFirestore.instance.collection('ideas').snapshots();
});

What do I do now? The rest of my code is depended on the ideasListProvider, so I will have to somehow provide it with the a list of the documents from the ideas collection on firebase.

Answer 1

Good news, you are on the right track. First, what you want to do is likely map your firestore data to your data model. This can be accomplished by creating a new stream mapped from your firestore data stream:

final firebaseIdeaProvider = StreamProvider.autoDispose<List<Idea>>((ref) {
  final stream = FirebaseFirestore.instance.collection('ideas').snapshots();
  return stream.map((snapshot) => snapshot.docs.map((doc) => Idea.fromJson(doc.data())).toList());
});

Now all that's left is to read your StreamProvider. An example that will handle loading, error, and new data states could be as follows (with hooks_riverpod ):

class IdeasExample extends HookWidget {
  const IdeasExample({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Ideas Example'),
      ),
      body: useProvider(firebaseIdeaProvider).when(
        loading: () => const Center(child: CircularProgressIndicator()),
        error: (err, stack) => Center(child: Text(err.toString())),
        data: (ideas) {
          return ListView.builder(
            itemCount: ideas.length,
            itemBuilder: (_, index) {
              return ListTile(
                title: Text(ideas[index].toString()),
              );
            },
          );
        },
      ),
    );
  }
}

Without hooks:

class IdeasExample extends ConsumerWidget {
  const IdeasExample({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context, ScopedReader watch) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Ideas Example'),
      ),
      body: watch(firebaseIdeaProvider).when(
        loading: () => const Center(child: CircularProgressIndicator()),
        error: (err, stack) => Center(child: Text(err.toString())),
        data: (ideas) {
          return ListView.builder(
            itemCount: ideas.length,
            itemBuilder: (_, index) {
              return ListTile(
                title: Text(ideas[index].toString()),
              );
            },
          );
        },
      ),
    );
  }
}