weird behaviour from the Text widget or from the dart anlysis not sure about flutter HOT 7 CLOSED

'$title' means essentially (title).toString(). And null.toString() is allowed, it just returns 'null' as you see.

Sure maybe a lint could be added though, just like we have one to prefer string templating rather than using + operator.

from flutter.

i was trying to reproduce that in dart :

void main() {
  final String? title;
  print('$title');
}

the dart analysis and the compiler doesn't allow this but flutter Text widget is allowing the null value to pass and so making the value appearing in the ui null , the problem is i why Text widget is allowing this behaviour ?

from flutter.

This completely correct behavior, your title variable in this snippet:

void main() {
  final String? title;
  print('$title');
}

title variable is in scope of main function so it will not allow to use if you doesn't assign it yet.

But in your flutter code:

class Home extends StatelessWidget {
  const Home({super.key, this.title});
  final String? title;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('$title'),
        centerTitle: true,
      ),
      body: Center(
        child: Text(
          '$title',
        ),
      ),
    );
  }
}

The title is param of Home widget so compiler confidently sure that is assigned (cuz you run the build function inHome widget so this must run through constructor of Home). And the "$title" is String interpolation it make any value to string so null to String is null so it right.

The solution easy that you accept only final String title; and handle the null case outside the Home widget.

from flutter.

I know that string templating in dart happens in run time not compile time the problem is why not to try adding this feature to the compiler to detect such cases

from flutter.

Also as far as i know in flutter :
Text('$title') same as Text(title)
This is when title is String
But when using String? the first one the only one allowed (even if there is a possibility for null case to pass )and second is rejected

from flutter.

Something more intersseting is for exemple :
'$title'.length doesn't throw a runtime exception and have a value of 1 😐?

from flutter.

I guess that's it

from flutter.