How to use the data from different model and context?

Question

I made the small app, and designed like this:

return MultiProvider(
     providers: [
         ChangeNotifierProvider(create: (context) => AModel()),
        ChangeNotifierProvider(create: (context) => BModel(),),
         ChangeNotifierProvider(create: (context) => CModel(),),
       ]

at first, need initialize config data in CModel, then move to AModel and add detailed data, in the A page like this:

Widget build(BuildContext context) {
     AModel aModel = Provider.of<AModel>(context);
     CModel cModel = Provider.of<CModel>(context);

after add the detailed data, anything goes well and the log:

 build aModel.chosenData.length 1   build cModel.chosenData.length 0  
 build aModel.allConfigs.length 0   build cModel.allConfigs.length 1

after force stop the app and re-open, the A page is crashed, and the log becomes:

build aModel.chosenData.length 1   build cModel.chosenData.length 0  
 build aModel.allConfigs.length 1   build cModel.allConfigs.length 0

My terrible design raised this issue, is there any solution to avoid this embarrassed situation ?

Answer 1

Very difficult to give an accurate answer with this info but if a provider depends on another, you can nest them, or control them from a third widget, and that may help you.

If A depends on C then build the widgets like

WidgetA build(BuildContext context) {
 AModel aModel = Provider.of<AModel>(context);
 

WidgetC build(BuildContext context) {
 AModel aModel = Provider.of<AModel>(context);
 

WidgetMain build(BuildContext context) {
 -- Do things with C
 -- When get a result from C do things with A.
 -- Be careful to validate the state here, you can use didChangeAppLifecycleState(AppLifecycleState state) to check closing of the app