CODEWITHSUNDEEP
arrayslistdart
dshukertjr
dshukertjr

Reputation: 18622

Get the first element of list if it exists in dart

I was wondering if there is a way to access the first element of a list in dart if an element exists at all, and otherwise return null.

First, I thought this would do the job:

final firstElement = myList?.first;

This works if myList is null or myList.length > 0, but would give me an error if myList is an empty List.

I guess I could do something like this:

final firstElement = (myList?.length ?? 0) > 0 ? myList.first : null;

But I was wondering if there is a simpler way of doing what I'm trying to do out there.

Upvotes: 36

Views: 40818

Answers (4)

Mrb83
Mrb83

Reputation: 130

Note List<T>.firstOrNull is available in Dart >= 3.0.0, package:collection no longer required.

Upvotes: 3

Edwin Liu
Edwin Liu

Reputation: 8025

UPDATE: since Dart 3.0, package:collection is no longer required to use method firstOrNull. Thanks to @Mrb83 for pointing this out.

Now you can import package:collection and use the extension method firstOrNull 

import 'package:collection/collection.dart';

void main() {

  final myList = [];

  final firstElement = myList.firstOrNull;

  print(firstElement); // null
}

Upvotes: 89

bartektartanus
bartektartanus

Reputation: 16080

For Dart 2.12 (with null-safety) adding an extension function might be a good idea:

extension MyIterable<T> on Iterable<T> {
  T? get firstOrNull => isEmpty ? null : first;

  T? firstWhereOrNull(bool Function(T element) test) {
    final list = where(test);
    return list.isEmpty ? null : list.first;
  }
}

Upvotes: 16

Dusk
Dusk

Reputation: 1877

As you may have already guessed, you need to implement such functionality yourself and since this and/or this are still open, there is no minimalistic version of doing it (i.e. through extension functions).

So we should do the longer version: 

E firstOrNull<E>(List<E> list) {
  return list == null || list.isEmpty ? null : list.first;
}

Edit: As mentioned by @Mattia there will be support for static extension functions in version 2.6 (currently in beta).

Upvotes: 1

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