prefer_is_empty
Use isEmpty
for Iterables and Maps.
This rule is available as of Dart 2.0.0.
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