samples/provider_shopper/README.md

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 section of 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
• StackOverflow

If you run into an issue with the sample itself, please file an issue in the main Flutter repo.