Where clauses in flutter firebase streams

Question

I'm setting up a category selector where pressing a certain image changes the category the user is supposed to see. however if the user doesn't pick a category he should see all items.

 FutureBuilder(
          future: _authService.getUserId(),
          builder: (context, snapshot) {
            if (snapshot.hasData)
              return StreamBuilder(
                  stream: _firestore
                      .collection('Item')
                      .where(_category != null ? ('category', isEqualTo: _category) : true)
                      .snapshots(),

I was trying to do something like this but it just gives me an error saying it was expecting a bracket somewhere..

Another question I have about this setup is, even if the _categoy changes, would that update the list? or since the stream is already built it won't? and in the latter, how would I come about updating the list with the actual values?

1) "it just gives me an error saying it was expecting a bracket somewhere.." Please edit your question to include the exact error message and (if this is a run time error) stack trace. 2) What is the value of _category. Please make sure the code can be run as is, so that everything needed is in the snippet. 3) Please limit yourself to a single question per post. — Frank van Puffelen
– Frank van Puffelen, Commented May 31, 2020 at 13:56

Peter Haddad · Accepted Answer · 2020-05-31 15:11:06Z

2

Change it to the following:

          StreamBuilder(
            stream: _category != null
                ? Firestore.instance
                    .collection('Item')
                    .where("category", isEqualTo: _category)
                    .snapshots()
                : Firestore.instance.collection('Item').snapshots(),
          ),

If the _category is not null then use the where clause, else retrieve everything inside Item.

edited May 31, 2020 at 15:11

answered May 31, 2020 at 14:09

Peter Haddad

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5 Comments

raiton Over a year ago

This works, however it wont show items that don't have the property "category"

Peter Haddad Over a year ago

If the where clause is failing then it won't show any data

Peter Haddad Over a year ago

The query will show items if category == _category(your variable). If a document doesn't satisfy that then it wont retrieve it

raiton Over a year ago

let's put it like this. I want to be able to filter by category but I want it to show all items and don't filter, if my _category == null

raiton Over a year ago

works like a charm, not sure why I didn't think of this. amazing :)

awaik · Accepted Answer · 2020-11-10 19:25:50Z

1

The actual answer is here https://stackoverflow.com/a/63293409/7198006

that is

Dont initialize streams in build method

Use StatefulWidget and initialize the stream in State.initState

answered Nov 10, 2020 at 19:25

awaik

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