use_enums

Use enums rather than classes that behave like enums.

Classes that look like enumerations should be declared as enums.

DO use enums where appropriate.

Candidates for enums are classes that:

• are concrete,
• are private or have only private generative constructors,
• have two or more static const fields with the same type as the class,
• have generative constructors that are only invoked at the top-level of the initialization expression of these static fields,
• do not define hashCode, ==, values or index,
• do not extend any class other than Object, and
• have no subclasses declared in the defining library.

To learn more about creating and using these enums, check out Declaring enhanced enums.

BAD:

class LogPriority {
  static const error = LogPriority._(1, 'Error');
  static const warning = LogPriority._(2, 'Warning');
  static const log = LogPriority._unknown('Log');
​
  final String prefix;
  final int priority;
  const LogPriority._(this.priority, this.prefix);
  const LogPriority._unknown(String prefix) : this._(-1, prefix);
}

GOOD:

enum LogPriority {
  error(1, 'Error'),
  warning(2, 'Warning'),
  log.unknown('Log');
​
  final String prefix;
  final int priority;
  const LogPriority(this.priority, this.prefix);
  const LogPriority.unknown(String prefix) : this(-1, prefix);
}

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

linter:
  rules:
    - use_enums

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

linter:
  rules:
    use_enums: true