Documentation comment references

Doc comments can contain references to various identifiers. Elements, such as functions and classes, can be referenced by wrapping their name in square brackets ([...]) in a doc comment (a comment starting with ///). Some examples:

/// Returns a [String].
String f() => 'Hello';

/// Wraps [object] with [Future.value].
Future<T> g<T>(T object) => Future.value(object);

These doc comments contain references to the String class, the object parameter, and the Future.value constructor.

There are several benefits to referring to code elements with doc comment references:

Doc comment references enable several IDE features:

• Code completion An element's name can be code-completed within square brackets.
• Rename refactoring When an element is renamed via an IDE command, the IDE can rewrite uses of that element, including references in doc comments.
• Find references When an IDE lists all "references" to an element, it can include references in doc comments.
• Go to definition An IDE can also provide Go-to-definition support at the location of a doc comment reference.

In API documentation generated by dart doc, a doc comment reference is linked, if possible, to the documentation page of the element being referenced. If the element does not have a documentation page (for example, a function parameter, a type parameter, or a private class), then no link is created.

Most library members can be referenced in a doc comment, including classes, constants, enums, named extensions, extension types, functions, mixins, and type aliases. This includes all in-scope library members, either declared locally, or imported. Library members that are imported with an import prefix can be referenced with the prefix. For example:

import 'dart:math' as math;

/// [List] is in scope.
/// So is [math.max].
int x = 7;

Most members of a class, an enum, an extension, an extension type, and a mixin can also be referenced. A reference to a member that is not in scope must be qualified (prefixed) with its container's name. For example the wait static method on the Future class can be referenced in a doc comment with [Future.wait]. This is true for instance members as well; the add method and the length property on the List class can be referenced with [List.add] and [List.length]. When container members are in-scope, such as in an instance method's doc comment, they can be referenced without the qualifying container name:

abstract class MyList<E> implements List<E> {
  /// Refer to [add] and [contains], which is declared on [Iterable].
  void myMethod() {}
}

Unnamed constructors can be referenced by using the new name, similar to the tear-off of an unnamed constructor. For example, [DateTime.new] is a reference to the unnamed DateTime constructor.

Parameters of a function and parameters of a function type can be referenced in a doc comment only when they are in scope. They can therefore only be referenced within a doc comment on such a parameter's function or on a type alias for such a parameter's enclosing function type.

Type parameters can be referenced in a doc comment only when they are in scope. Therefore, a type parameter of a method, top-level function, or type alias can only be referenced within a doc comment on that element, and a type parameter of a class, enum, extension, extension type, and mixin can only be referenced within a doc comment on that element or on one of its members.

The doc comment for a type alias that aliases a class, enum, extension type, or mixin can't reference any of the aliased type's members as if they were in scope.

Unless stated otherwise, the documentation on this site reflects Dart 3.6.0. Page last updated on 2024-10-10. View source or report an issue.