You can use pub to manage Dart packages.
At the very minimum, a Dart package is simply a directory containing a pubspec file.
The pubspec contains some metadata about the package. Additionally, a package can contain dependencies (listed in the pubspec), Dart libraries, command-line apps, web apps, resources, tests, images, or examples. If your app uses one or more packages, then your app itself must be a package.
A package can live anywhere. For example, some packages are on GitHub. The Dart team publishes packages at pub.dartlang.org, and we hope you will, too.
To use a library that is in a Dart package, you need to do the following:
To use a package, your application must define a pubspec. The simplest possible pubspec lists only the package name:
A pubspec is where you list dependencies and their download locations.
The pubspec is a file named
pubspec.yaml, and it
must be in the top directory of your application.
Here is an example of a pubspec that specifies the locations of two packages. First, it points to the js package that is hosted on pub.dartlang.org, and then it points to the intl package in the Dart SDK:
name: my_app dependencies: js: any intl: any
For details, see the pubspec documentation and the documentation for the packages you are interested in using.
Once you have a pubspec, you can run
get from the top directory of your application:
cd <path to my_app> pub get
This process is called “getting the dependencies”.
command determines which packages your app depends on, and
puts them in a central cache. For git dependencies, pub clones the git
repository. For hosted dependencies, pub downloads the package from
pub.dartlang.org. Transitive dependencies are included, too. For
example, if the js package depends on the test package,
grabs both the js package and the test package.
Finally, pub creates a
directory (under your app’s top directory) that has links to the
packages that your app depends on.
To import libraries found in packages, use the
import 'package:js/js.dart' as js; import 'package:intl/intl.dart';
The Dart runtime takes everything after
and looks it up within the
packages directory for
You can also use this style to import libraries from within your own package.
Consider the following pubspec file which declares a dependency on
name: my_app dependencies: transmogrify:
Let’s say that your package is laid out as follows:
transmogrify/ lib/ transmogrify.dart parser.dart test/ parser/ parser_test.dart
parser_test file could import
parser.dart like this:
But that’s a fragile relative path. If
parser_test.dart is ever moved
up or down a directory, that path will break and you’ll have to fix the code.
Instead, you can do as follows:
This way, the import can always get to
parser.dart regardless of where the
importing file is.
The first time you get a new dependency for your package, pub will download the
latest version of it that’s compatible with your other dependencies. It then
locks your package to always use that version by creating a lockfile.
This is a file named
pubspec.lock that pub creates and stores next to your
pubspec. It lists the specific versions of each dependency (immediate and
transitive) that your package uses.
If this is an application package, you will check this file into source control. That way, everyone working on your app ensures they are using the same versions of all of the packages. This also makes sure you use the same versions of code when you deploy your app to production.
When you are ready to upgrade your dependencies to the latest versions, do:
$ pub upgrade
This tells pub to regenerate the lockfile using the newest available versions of your package’s dependencies. If you only want to upgrade a specific dependency, you can specify that too:
$ pub upgrade transmogrify
transmogrify to the latest version but leaves everything else