Dart check if many variable is null

Question

Hello im new in dart language, is someone can help me to write this condition better, it works but it's a lot repetitive and i feel theres a better ways to write it :

 if (var1 != null || var2 != null || var3 != null || var4 != null || var5 != null){ ShowMyWidget }

thank you.

looks fine to me but if you had more variables you could push them into a Map and then create a map that loops through the Map to check if null for each object in the map — mister_cool_beans
– mister_cool_beans, Commented Dec 28, 2021 at 19:49

zgorawski · Accepted Answer · 2023-01-30 15:33:36Z

4

if (![var1, var2, var3, var4, var5].contains(null)){ ShowMyWidget }

answered Jan 30, 2023 at 15:33

zgorawski

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1 Comment

Berke Uğur Over a year ago

It hadn't occurred to me before. Thanks, now my codes will be more organized.

jamesdlin · Accepted Answer · 2021-12-28 20:52:10Z

2

If you really want, you could do:

if ([var1, var2, var3, var4, var5].any((x) => x != null)) {
  ShowMyWidget();
}

answered Dec 28, 2021 at 20:52

jamesdlin

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Comments

Robert Pietraru · Accepted Answer · 2021-12-28 19:53:32Z

Rather than checking all those variables, I'd make them optional parameters to the widget. If you do that, you can just check if they're null using null-safety inside it, whenever you actually need them.

class TestWidget extends StatelessWidget {
  final String? testPar1;
  final String? testPar2;
  final String? testPar3;
  final String? testPar4;
  const TestWidget({
    this.testPar1,
    this.testPar2,
    this.testPar3,
    this.testPar4,
    Key? key,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        Text(testPar1 ?? 'nope'),
        Text(testPar2 ?? 'nope'),
        Text(testPar3 ?? 'nope'),
        Text(testPar4 ?? 'nope'),
      ],
    );
  }
}

Keep in mind that your way of doing it isn't wrong.

Pierre Huret · Accepted Answer · 2021-12-29 20:29:22Z

0

ok thanks you your answers, I'll explain my goal a litle bit more : I have a detail page in may app with many custom widget and i want to check if the variables inside my widgets are null in order to either show or hide it.

My app screenshot

So here for exemple I wanna check if one of the booking link isn't null to display the title.

if (link1 != null || link2 != null || link3 != null || link4 != null || var5 != null){ ShowMyTitle }

answered Dec 29, 2021 at 20:29

Pierre Huret

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1 Comment

Community Over a year ago

As it’s currently written, your answer is unclear. Please edit to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers in the help center.

Dartist · Accepted Answer · 2024-04-16 11:28:14Z

0

When testing a lot of variables for non-nullity, it's better to put them into an array and use the nonNulls property:

 if ([var1, var2, var3, var4, var5].nonNulls.isNotEmpty) {
    ShowMyWidget();
  }

Using the nonNulls property, it will also become easy to just process the ones that you need to display:

[link1, link2, link3, link4, link5].nonNulls.forEach((link) => ShowMyWidget(link));

Or shorter, if the parameter of ShowMyWidget is the same type as your links:

[link1, link2, link3, link4, link5].nonNulls.forEach(ShowMyWidget);

answered Apr 16, 2024 at 11:28

Dartist

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