How to execute function when a variable is not null Flutter

Question

I have this code in _MyAppState in my main.dart :

     var _p3provider;
     @override
      void initState() {
        super.initState();
        P3provider p3provider = new P3provider();
        authentification(p3provider);
        _p3provider = p3provider;
      }

I pass the variable _p3provider as p3provider to MyHomePage statefulWidget of my main.dart,

Here is some code of _MyHomePageState :

void initState() {
    super.initState();
    if (widget.p3provider.jsession_id == null) {
      Future.delayed(Duration(seconds: 2), (){
        getTasks();
      }); 
    } else {
      getTasks();
    }
  }

To execute my getTasks function I need the jsession_id variable from p3provider object to be initialized. This variable is initialized in the initState of _MyAppState at this line : authentification(p3provider); .

The problem is that both the initState of _MyAppState and _MyHomePageState are executed at the same time so if I directly call getTasks() in the initState of _MyHomePageState it will return an error because p3provider.jsession_id will not have been initialized yet.

To avoid this error I used a Future.delayed after a checking if the variable is null, but I don't think this solution is optimal, I would like the function getTasks() to be executed directly when jsession_id become not null.

If anyone has an idea on how to do this, you are more than welcome ! :)

Just tried it, thanks, Future.then((widget.p3provider.jsession_id){ getTasks(); }); but put me an error doesn't recognize widget.p3provider.jsession_id and says "instance member then can't be accessed using static access" — JS1, Nov 16 '21 at 13:17
you were to fast bro, it didn't work actually I posted my comment by error while redacting it — JS1, Nov 16 '21 at 13:21
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/239278/discussion-between-diwyansh-and-js1). — Diwyansh, Nov 16 '21 at 13:30

score 0 · Accepted Answer · answered Nov 22 '21 at 10:28

Found a solution :

I define this class :

class HomePageController{
  var getTasks;
}

Which I instanciate in _MyAppState :

final HomePageController myController = HomePageController();

I pass it down to MyHomePage widget :

home: MyHomePage(controller: myController),

And in the initState of _MyHomePageState I assign my function getTasks() to the controller variable getTasks :

@override
  void initState() {
    super.initState();
    widget.controller.getTasks = getTasks;
  }

Now I can execute getTasks via the controller in _MyAppState :

@override
  void initState(){
    super.initState();
    authentification().then((value){
      myController.getTasks();
  }

Here is the topic where I got it : Flutter calling child class function from parent class

How to execute function when a variable is not null Flutter

1 Answers1