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2022-10-10 08:58:58 +02:00

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# sync_router
This example uses **synchronous redirects** while exploiting a `ChangeNotifier` as a `Listenable` object inside our Router definition.
**Dependencies**:
- GoRouter v5
- Riverpod v2
## Is this approach advised?
This example just works. It has its downside (see below), but it correctly exploits GoRouter's API, while still maintaining Riverpod's advantages.
**Advantages:**
- `RouterNotifier` centralizes all the logic, which can be highly customizable
- `ref.listen` allows to scale reactive dependencies linearly
- No side effects
**Disadvantages:**
- `ChangeNotifier` is discouraged within Riverpod (see https://riverpod.dev/docs/concepts/providers/#different-types-of-providers), but it's the closest class we have at our disposal that implements the `Listenable` interface (as required by `GoRouter`'s `refreshListenable` parameter);
- A `ref` object _must_ be piped down to `ChangeNotifier`: this might be undesirable, as this causes a small caveat (see below)
### Short explanation
In this example we directly implement a `ChangeNotifier`. In its constructor method, we exploit `ref.listen` to add reactive dependencies through `notifyListeners`.
**Caveat**
Reactive dependencies must be defined _only_ within the constructor and _only_ through `ref.listen`.
This is key to avoid unnecessary rebuilds: when writing logic inside our Notifier, we might want to use `ref.read` to read providers, _and avoid `ref.watch`_.
GoRouter is already aware of state changes through `refreshListenable`: we don't want to trigger a rebuild of the surrounding provider.
_Simply put - this is not clean code - this works because of side effects._
## Getting started
First, read the code:
- 'lib/main.dart' has UI elements
- 'lib/router.dart' has the routing logic
- 'lib/auth.dart' has the auth logic
Most of the actions are mocked, here.
Then, run:
`flutter test`
`flutter run`
Enjoy!