title: By refrence or by value in flutter
body: <p>Is the flutter functions (methods?) parameters are &quot;by value&quot; of &quot;by reference&quot;?
  Does different variable types have different approach ?
  for example(s)</p>
  <pre><code>1)   BlocProvider.of&lt;CounterCubit&gt;(context).dec();
  2)   const MyApp({Key? key}) : super(key: key);
  3)   CounterState(counterValue: state.counterValue+1)
  4)   CounterState(counterClass: ClassA)
  </code></pre>
  <p>Another sample in following code:</p>
  <pre><code>@override
    Widget build(BuildContext context) {
      return Scaffold(
        appBar: AppBar(
          title: Text(widget.title),
        ),
       ...
  </code></pre>
  <p>where the context variable value is created, does inside the build function and only after the returning from the build function the context has value, or somewhere else before...?
  Does the value of context variable before entering the build function is defined? where ?</p>