Best place to do a check for auth session is still alive in flutter - flutter

Question

I am building an app which is using native (iOS and Android) framework to do an authentication. I created a plugin which wraps all framework exposed methods to flutter. I have to check every screen change that user is authenticated and session is alive and if not call framework to do so, what will be the best place in flutter to do such check?

Answer 1

Inside a widget.
Widgets are nearly always where you want to put your logic.
To be exact, what you want is a StatefulWidget that expose an InheritedWidget using a custom static MyInheritedWidget of(BuildContext context) method. InheritedWidget which will possess all the login informations and a few "onChange" methods.
You will then be able to access anywhere inside your app to this InheritedWidget using MyAuth.of(context) and therefore have access to all the needed data.
Usually you'll end up with this :
/// The user data model. May be serializable. Usually immutable
#immutable
class MyUser {
const MyUser({this.name});
final String name;
}
/// The entry point of your global logic.
/// Most of the time, will only take one child as parameter
/// and nothing else. And will also expose a [of] method
class MyAuth extends StatefulWidget {
final Widget child;
const MyAuth({this.child});
/// Fetch the closest [_MyInheritedAuth] from the widget tree
/// using context. And bind the widget possessing that context
/// to reload evytimes the inherited widget changes
static _MyInheritedAuth of(BuildContext context) {
final _MyInheritedAuth inherited = context.inheritFromWidgetOfExactType(_MyInheritedAuth);
return inherited;
}
#override
_MyAuthState createState() => new _MyAuthState();
}
typedef void MyUserNameChange(String name);
/// Your controller. Will handle all the logic and just
/// pass it all to [_MyInheritedAuth]
class _MyAuthState extends State<MyAuth> {
MyUser user;
#override
initState() {
super.initState();
user = const MyUser(name: 'foo');
}
void onUserNameChange(String name) {
setState(() {
user = new MyUser(name: name);
});
}
#override
Widget build(BuildContext context) {
return new _MyInheritedAuth(user: user, editUserName: onUserNameChange, child: widget.child,);
}
}
/// What the other widgets will get when user [MyAuth.of].
/// Inherit from [InheritedWidget] to be able to bind a context
/// to this widget's updates/
class _MyInheritedAuth extends InheritedWidget {
final MyUser user;
final MyUserNameChange editUserName;
const _MyInheritedAuth({ #required this.user, #required this.editUserName, #required Widget child,}): super(child: child);
#override
bool updateShouldNotify(_MyInheritedAuth oldWidget) {
return user != oldWidget.user || editUserName != oldWidget.editUserName;
}
}
And whenever you need to use user infos, you can just do MyAuth.of(context).user.