use_enums.md

Pattern: Missing use of enum

Issue: -

Description

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.

Example of incorrect code:

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);
}

Example of correct code:

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);
}

Further Reading

• Linter for Dart - use_enums