Make your sorts readable with functional by-field comparators

Dart Tests Pub package Package publisher

The comparators package is a toolset for creating Java-like comparators in Dart, designed to provide a way
to compare objects by their fields. It also provides a declarative way to combine comparators sequentially.

Features

Import comparators/comparators.dart to use:

  • By-field object comparators
  • Boolean comparison
  • Combining comparators to break ties

Comparator extensions then and reversed from this package are deprecated and will be removed in 2.0.0. Please, use the analogues from the package:collection: then and inverse.

In 2.0.0, this package will export those instead of the removed ones.

Getting Started

To install the package, run pub add comparators or add the following line to your pubspec.yaml:

dependencies:
  # other dependencies
  comparators: ^<version>

Usage

The following utility functions can be imported from the comparators/comparators.dart file.

Comparison by a single field:

// this will sort the list by the username field of the User object
users.sort(compare((u) => u.username));

Comparison by a boolean field:

users.sort(compareBool((u) => u.isActive));

When comparing boolean, the function will use the integer comparison and the following transformation: true => 1, false => 0.

Combining comparators to compare sequentially:

users.sort(compareSequentially([
    compare((user) => user.name),
    compare((user) => user.surname),
    compare((user) => user.country),
]));

In this example, user objects will be compared by a name first, then by a surname, and by a country.

The same result could be achieved using comparator chaining from the package:collection, but in a less declarative way:

users.sort(
  compare((User user) => user.name).then(
    compare((User user) => user.surname).then(
      compare((User user) => user.country),
    ),
  ),
);

Also, note that the compiler cannot infer types in the example with chaining, but can with compareSequentially.

Issues and contributions

If you found any issues or would like to contribute to this package, feel free to do so at the project's GitHub. Contributions are welcome - start the discussion in the Issue tracker.

Libraries

comparators
extensions