use_enums

Use enums rather than classes that behave like enums.

This rule is available as of Dart 2.17.0.

This rule has a quick fix available.

Details

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.

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);
}

Usage

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

linter:
  rules:
    - use_enums