prefer_final_in_for_each

Prefer final in for-each loop variable if reference is not reassigned.

DO prefer declaring for-each loop variables as final if they are not reassigned later in the code.

Declaring for-each loop variables as final when possible is a good practice because it helps avoid accidental reassignments and allows the compiler to do optimizations.

BAD:

for (var element in elements) { // LINT
  print('Element: $element');
}

GOOD:

for (final element in elements) {
  print('Element: $element');
}

GOOD:

for (var element in elements) {
  element = element + element;
  print('Element: $element');
}

The prefer_final_in_for_each rule is incompatible with the following rules:

• unnecessary_final

To enable the prefer_final_in_for_each rule, add prefer_final_in_for_each under linter > rules in your analysis_options.yaml file:

linter:
  rules:
    - prefer_final_in_for_each

If you're instead using the YAML map syntax to configure linter rules, add prefer_final_in_for_each: true under linter > rules:

linter:
  rules:
    prefer_final_in_for_each: true

Unless stated otherwise, the documentation on this site reflects Dart 3.6.2. Page last updated on 2025-01-27. View source or report an issue.