Get InheritedWidget parameter in initState

Question

i need some help understanding how to obtain data from inherited widget.

I usually get the parameter from my widget directly from the build method using

  @override
  Widget build(BuildContext context) {    
   //THIS METHOD
   var data = StateContainer.of(context).data;

   return Container(child:Text("${data.parameter}"));
  }

But this method cant be called from initState since there is no buildContext yet.

I need in the initState method to have that parameter (i call my fetch from server in that and i need to pass that data to my function), so, how should i do it?

@override
void initState() {
 otherData = fetchData(data);
 super.initState();
}

I tried using didChangeDipendencies() but it is called every time the view is rebuilt (popping from screen, etc.) so it is not what i want to use and neither the FutureBuilder widget.

Any suggestion?

Answer 1

First, note that you probably do want to use didChangeDependencies. But you can't just do your call there without any check. You need to wrap it in an if first.

A typical didChangeDependencies implementation should look similar to:

Foo foo;

@override
void didChangeDependencies() {
  super.didChangeDependencies();
  final foo = Foo.of(context);
  if (this.foo != foo) {
    this.foo = foo;
    foo.doSomething();
  }
}

Using such code, doSomething will be executed only when foo changes.

---

Alternatively, if you are lazy and know for sure that your object will never ever change, there's another solution.

To obtain an InheritedWidget, the method typically used is:

BuildContext context;
InheritedWidget foo = context.inheritFromWidgetOfExactType(Foo);

and it is this method that cannot be called inside initState.

But there's another method that does the same thing:

BuildContext context;
InheritedWidget foo = context.ancestorInheritedElementForWidgetOfExactType(Foo)?.widget;

The twist is: - this method can be called inside initState - it won't handle the scenario where the value changed.

So if your value never changes, you can use that instead.