Flutter 给 Streambuilder initalData

Question

I have a Streambuilder that takes Firebase Firestore snapshot as a Stream and I would like to add initalData to the Streambuilder .

How can I pass initalData to the Streambuilder ?

The Code:

StreamBuilder(
  stream: FirebaseFirestore.instance
      .collection("events")
      .snapshots(),
  builder: (BuildContext ctx, AsyncSnapshot<QuerySnapshot> snapshot) {
    if (!snapshot.hasData || snapshot.data.docs.isEmpty) {
      return NoDataRelatedLocation();
    }
    if (snapshot.hasError) {
      return Text(snapshot.error.toString());
    } else {
      return new RelatedLocationListing(
        relatedLocationList: snapshot.data.docs,
      );
    }
  },
),

Answer 1

You can add initialData to StreamBuilder :

StreamBuilder(
   initialData: ..... // <~~~ add it here. 
   stream: ... 
   builder: ...

You just need to make sure that your initialData matches that type of data coming from the stream. Since QuerySnapshot is a Firebase specific type, you should map your stream to a data type that you can create and that's known to you.

Here's a pseudo code:

initialData: [MyDataType()],
stream: FirebaseFirestore.instance
      .collection("events")
      .snapshots().map((snapshot) => MyDataType.fromMap(snapshot.doc));