A common use-case when using providers is to want to destroy the state of a provider when it is no-longer used.
There are multiple reasons for doing such, such as:
- When using Firebase, to close the connection and avoid unnecessary cost
- To reset the state when the user leaves a screen and re-enters it.
Providers comes with a built-in support for such use-case, through the
To tell Riverpod to destroy the state of a provider when it is no-longer used,
.autoDispose to your provider:
That's it. Now, the state of
userProvider will automatically be destroyed
when it is no-longer used.
Note how the generic parameters are passed after
autoDispose instead of before –
autoDispose is not a named constructor.
You can combine
.autoDispose with other modifiers if you need to:
Marking a provider with
autoDispose also adds an extra property on
maintainState property is a boolean (
false by default) that allows
the provider to tell Riverpod if the state of the provider should be preserved
even if no-longer listened.
A use-case would be to set this flag to
true after an HTTP request have
This way, if the request failed and the user leaves the screen then re-enters it, then the request will be performed again. But if the request completed successfuly, the state will be preserved and re-entering the screen will not trigger a new request.
autoDispose modifier could be combined with FutureProvider and
to easily cancel HTTP requests when they are no-longer needed.
The goal is:
- Start an HTTP request when the user enters a screen
- if the user leaves the screen before the request completed, cancels the HTTP request
- if the request succeeded, leaving and re-entering the screen does not start a new request
In code, this would be:
.autoDispose, you may find yourself in a situation where your
application does not compile with an error similar to:
The argument type 'AutoDisposeProvider' can't be assigned to the parameter type 'AlwaysAliveProviderBase'
Don't worry! This error is voluntary. It happens because you most likely have a bug:
You tried to listen to a provider marked with
.autoDispose in a provider that
is not marked with
.autoDispose, such as:
This is undesired, as it would cause
firstProvider to never be disposed.
To fix, consider marking