Right place for ref.listen() in ConsumerStatefulWidget

[topperspal]

This time, the "ref" isn't passed as parameter of the build method, but is rather a property of the ConsumerState object:

But when I use ref.listen() in initState() it throws the following error :-

ref.listen can only be used in build method of ConsumerState

The question is that if I cannot use ref.listen() in init state then where I should place it in the class.

[daniellampl]

Place it at the beginning of the build method. It won't force your widget to rebuild if the provider updates its state. It just executes the callback you pass into it.

[topperspal]

It add a new listener each time when build metod is called.

…

On Fri, Nov 12, 2021, 2:37 AM Daniel Lampl ***@***.***> wrote: Place it at the beginning of the build method. It won't force your widget to rebuild if the provider updates its state. It just executes the callback you pass into it. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#915 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AT2OE2SRTHM4KPFT62IKDEDULQWCBANCNFSM5H2YWBPQ> . Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>.

[daniellampl]

ConsumerWidget actually takes care of closing previously opened provider listening subscriptions before it subscribes to them again. So when the widget rebuilds, the subscriptions get closed and resubscribed automatically.

@rrousselGit this should probably get mentioned in the documentation. What do you think?

[rrousselGit]

Closing in favor of #1370 and #1034. The former should allow initState to listen to providers, while the later will catch bugs where ref.listen is misused.

[ciriousjoker]

@rrousselGit

What's the state of this? The docs still warn against using listen in initState, but there's no reason given. The linter you mentioned also doesn't complain about using listen in initState.

Are we supposed to use listen in initState or build?

Use case: provider contains a bool for muting audio. When the provider value changes, we want to update the widget's audiocontroller with the new volume.

Sorry for pinging, I just checked the dartDoc for listen and it explains everything.

[feronetick]

@rrousselGit

What's the state of this? The docs still warn against using listen in initState, but there's no reason given. The linter you mentioned also doesn't complain about using listen in initState.

Are we supposed to use listen in initState or build?

Use case: provider contains a bool for muting audio. When the provider value changes, we want to update the widget's audiocontroller with the new volume.

If you want to listen provider changes in initState you can use ref.listenManual method with fireImmediately flag

[ciriousjoker]

Ah ok, so I guess for simple use cases like this, listenManual is the way to go. Unsubscribing & recreating the subscription seems like a waste to me even if it's done automatically.

Thanks a lot!