prefer_is_empty
Use isEmpty
for Iterable
s and Map
s.
This rule is available as of Dart 2.0.
Rule sets: core, recommended, flutter
This rule has a quick fix available.
Details
#DON'T use length
to see if a collection is empty.
The Iterable
contract does not require that a collection know its length or be able to provide it in constant time. Calling length
just to see if the collection contains anything can be painfully slow.
Instead, there are faster and more readable getters: isEmpty
and isNotEmpty
. Use the one that doesn't require you to negate the result.
BAD:
if (lunchBox.length == 0) return 'so hungry...';
if (words.length != 0) return words.join(' ');
GOOD:
if (lunchBox.isEmpty) return 'so hungry...';
if (words.isNotEmpty) return words.join(' ');
Usage
#To enable the prefer_is_empty
rule, add prefer_is_empty
under linter > rules in your analysis_options.yaml
file:
linter:
rules:
- prefer_is_empty
Unless stated otherwise, the documentation on this site reflects Dart 3.5.3. Page last updated on 2024-07-03. View source or report an issue.