StreamBuilder with Cloud Firestore bad practice?

Question

This StackOverflow answer (How to deal with unwanted widget build?) says that widgets should have no side effects in their build function, and that when using a StreamBuilder, you should not create a stream inline, but initialize in initState in a StatefulWidget.

However, the official cloud_firestore docs show this example:

This example creates the stream in the build function.

Is this truly bad practice, and the Firestore team is just wrong here, or is Firestore doing something under the hood that I don't know about that makes this okay?

score 1 · Accepted Answer · answered May 28 '20 at 00:55

1

This practice is perfectly normal. The post that you linked to doesn't say not to create Streams inline. That is only applicable for Futures and is made clear by the Flutter Docs in the FutureBuidler class.

answered May 28 '20 at 00:55

Christopher Moore

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Doesn't a stream do the same thing in principle though, which is create a side effect? – TransmissionsDev May 28 '20 at 00:58
@TransmissionsDev No because stream are intended to provide multiple values. – Christopher Moore May 28 '20 at 01:04
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Does StreamBuilder automatically call cancel() or something on the stream when rebuilding, otherwise, wouldn't it keep creating new streams each time it rebuilds, which would leak memory? – TransmissionsDev May 28 '20 at 01:04
@TransmissionsDev Not sure about that but it would definitely be cleaned by the garbage collector. Memory leaks aren't really a worry with these high-level languages. – Christopher Moore May 28 '20 at 01:05

StreamBuilder with Cloud Firestore bad practice?

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