How to access to provider field from class that do not have context?

Issue

I am using Provider. I have got two classes: class TenderApiData {} it's stand alone class (not widget). How I can write accesstoken to AppState?

class AppState extends ChangeNotifier // putted to ChangeNotifierProvider
{ 
  String _accesstoken; // need to fill not from widget but from stand alone class
  String _customer; // Fill from widget 
  List<String> _regions; // Fill from widget 
  List<String> _industry; // Fill from widget 
  ...
}

I need way to read\write accesstoken from stand alone classes.

Or I have issue with architecture of my app?

Here is full source code.

Solution

You cannot and should not access providers outside of the widget tree.

Even if you could theoretically use globals/singletons or an alternative like get_it, don't do that.

You will instead want to use a widget to do the bridge between your provider, and your model.

This is usually achieved through the didChangeDependencies life-cycle, like so:

class MyState extends State<T> {
  MyModel model = MyModel();

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    model.valueThatComesFromAProvider = Provider.of<MyDependency>(context);
  }
}

provider comes with a widget built-in widgets that help with common scenarios, that are:

• ProxyProvider
• ChangeNotifierProxyProvider

A typical example would be:

ChangeNotifierProxyProvider<TenderApiData, AppState>(
  initialBuilder: () => AppState(),
  builder: (_, tender, model) => model
    ..accessToken = tender.accessToken,
  child: ...,
);

Answered By - Rémi Rousselet