prefer_final_locals

Prefer final for variable declarations if they are not reassigned.

This rule is available as of Dart 2.0.

This rule has a quick fix available.

Incompatible rules: unnecessary_final

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

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

BAD:

void badMethod() {
  var label = 'hola mundo! badMethod'; // LINT
  print(label);
}

GOOD:

void goodMethod() {
  final label = 'hola mundo! goodMethod';
  print(label);
}

GOOD:

void mutableCase() {
  var label = 'hola mundo! mutableCase';
  print(label);
  label = 'hello world';
  print(label);
}

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

linter:
  rules:
    - prefer_final_locals

Unless stated otherwise, the documentation on this site reflects Dart 3.6.0. Page last updated on 2024-07-03. View source or report an issue.