no_ leading_ underscores_ for_ local_ identifiers
Avoid leading underscores for local identifiers.
Details
#
DON'T
use a leading underscore for identifiers that aren't private. Dart
uses a leading underscore in an identifier to mark members and top-level
declarations as private. This trains users to associate a leading underscore
with one of those kinds of declarations. They see
_
and think "private".
There is no concept of "private" for local variables or parameters. When one of
those has a name that starts with an underscore, it sends a confusing signal to
the reader. To avoid that, don't use leading underscores in those names.
EXCEPTION:: An unused parameter can be named
_
,
__
,
___
, etc. This is
common practice in callbacks where you are passed a value but you don't need
to use it. Giving it a name that consists solely of underscores is the idiomatic
way to indicate that the value isn't used.
BAD:
void print(String _name) {
var _size = _name.length;
...
}
GOOD:
void print(String name) {
var size = name.length;
...
}
OK:
[1,2,3].map((_) => print('Hello'));
Enable
#
To enable the
no_leading_underscores_for_local_identifiers
rule, add
no_leading_underscores_for_local_identifiers
under
linter > rules
in your
analysis_options.yaml
file:
linter:
rules:
- no_leading_underscores_for_local_identifiers
If you're instead using the YAML map syntax to configure linter rules,
add
no_leading_underscores_for_local_identifiers: true
under
linter > rules:
linter:
rules:
no_leading_underscores_for_local_identifiers: true
Unless stated otherwise, the documentation on this site reflects Dart 3.9.2. Report an issue.