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prefer_getter_over_method

v1.0.0 Warning Code Quality

This rule flags a no-argument method whose body only reads a value, where a getter reads as the property it is.

Why use this rule

Section titled “Why use this rule”

order.getTotal() and order.total return the same thing, but only the second reads as a property of the order. Effective Dart’s rule is that a member doing no real work and taking no arguments should be a getter; the empty parentheses otherwise suggest something happens when you call it.

This rule is in the pedantic preset, because where the line falls between “a property” and “a call” is a genuine API-design judgement.

See also: Effective Dart: prefer a getter

Don’t

Section titled “Don’t”
class Order {
  const Order(this.lineTotal, this.taxRate);


  final int lineTotal;
  final double taxRate;


  int tax() => (lineTotal * taxRate).round();


  bool isEmpty() => lineTotal == 0;
}

Do

Section titled “Do”
class Order {
  const Order(this.lineTotal, this.taxRate);


  final int lineTotal;
  final double taxRate;


  int get tax => (lineTotal * taxRate).round();


  bool get isEmpty => lineTotal == 0;
}

Call sites lose the parentheses: order.tax, order.isEmpty.

Known limitations

Section titled “Known limitations”

Only an expression body built from field reads and operators is reported. Everything below keeps its parentheses:

A body that calls anything. Clock.now() answers differently on each call, and a getter promises a stable property. This includes constructing an object:

class Session {
  const Session(this.startedAt);


  final DateTime startedAt;


  // Not reported: the body calls something.
  Duration age() => DateTime.now().difference(startedAt);


  // Not reported: the body allocates.
  List<String> tags() => <String>['a', 'b'];
}

A conventional name. toJson, toMap, toString, noSuchMethod, call, copyWith, toList and toSet are shapes a reader expects invoked.

A Stream or Future return type, and any async or generator body. A stream is something you subscribe to, not a property you read, so watchUser() keeps its parentheses.

A block body. It may be doing the work the parentheses promise, so int total() { return _amount; } is left alone.

A void method (called for an effect), an @override (which must keep the supertype’s shape), a generic method (a getter cannot take type arguments), an operator, and any method with a missing return type annotation.

Top-level functions are never reported — only methods on a class, mixin or extension.

Enabling this rule

Section titled “Enabling this rule”

This rule is in the pedantic preset, so it is enabled by preset: pedantic or by name:

many_lints.yaml
rules:
  prefer_getter_over_method:
    enabled: true

Turning this rule off

Section titled “Turning this rule off”

To disable this rule:

many_lints.yaml
rules:
  prefer_getter_over_method: false

To keep the rule on but skip certain paths, use per-rule exclude.

Section titled “Related rules”