mirror of https://github.com/flutter/samples.git
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
53 lines
2.1 KiB
53 lines
2.1 KiB
5 years ago
|
# provider_shopper
|
||
|
|
|
||
|
|
A Flutter sample app that shows a state management approach using the [Provider][] package.
|
||
|
|
This is the app discussed in the [Simple app state management][simple] section of
|
||
|
|
[flutter.dev][].
|
||
|
|
|
||
|
|
[Provider]: https://pub.dev/packages/provider
|
||
|
|
[simple]: https://flutter.dev/docs/development/data-and-backend/state-mgmt/simple
|
||
|
|
[flutter.dev]: https://flutter.dev/
|
||
|
|
|
||
|
|
## Goals for this sample
|
||
|
|
|
||
|
|
* Show simple use of `Provider` for providing an immutable value to a subtree
|
||
|
|
* Illustrate a simple state management approach using the ChangeNotifier class
|
||
|
|
* Show use of `ProxyProvider` for provided objects that depend on other provided objects
|
||
|
|
|
||
|
|
## The important bits
|
||
|
|
|
||
|
|
### `lib/main.dart`
|
||
|
|
|
||
|
|
Here the app sets up objects it needs to track state: a catalog and a shopping cart. It builds
|
||
|
|
a `MultiProvider` to provide both objects at once to widgets further down the tree.
|
||
|
|
|
||
|
|
The `CartModel` instance is provided using a `ChangeNotifierProxyProvider`, which combines
|
||
|
|
two types of functionality:
|
||
|
|
|
||
|
|
1. It will automatically subscribe to changes in `CartModel` (if you only want this functionality
|
||
|
|
simply use `ChangeNotifierProvider`).
|
||
|
|
2. It takes the value of a previously provided object (in this case, `CatalogModel`, provided
|
||
|
|
just above), and uses it to build the value of `CartModel` (if you only want
|
||
|
|
_this_ functionality, simply use `ProxyProvider`).
|
||
|
|
|
||
|
|
### `lib/models/*`
|
||
|
|
|
||
|
|
This directory contains the model classes that are provided in `main.dart`. These classes
|
||
|
|
represent the app state.
|
||
|
|
|
||
|
|
### `lib/screens/*`
|
||
|
|
|
||
|
|
This directory contains widgets used to construct the two screens of the app: the catalog and
|
||
|
|
the cart. These widgets have access to the current state of both the catalog and the cart
|
||
|
|
via `Provider.of`.
|
||
|
|
|
||
|
|
## Questions/issues
|
||
|
|
|
||
|
|
If you have a general question about Provider, the best places to go are:
|
||
|
|
|
||
|
|
* [Provider documentation](https://pub.dev/documentation/provider/latest/)
|
||
|
|
* [StackOverflow](https://stackoverflow.com/questions/tagged/flutter)
|
||
|
|
|
||
|
|
If you run into an issue with the sample itself, please file an issue
|
||
|
|
in the [main Flutter repo](https://github.com/flutter/flutter/issues).
|