Features

Submitted by jason on Fri, 03/13/2009 - 13:02

The features module enables the capture and management of features in Drupal. A feature is a collection of Drupal entities which taken together satisfy a certain use-case.

Features provides a UI and API for taking different site building components from modules with exportables and bundling them together in a single feature module. A feature module is like any other Drupal module except that it declares its components (e.g. views, contexts, CCK fields, etc.) in its .info file so that it can be checked, updated, or reverted programmatically.

Examples of features might be:

A blog
A pressroom
An image gallery
An e-commerce t-shirt store

Basic usage

Features is geared toward usage by developers and site builders. It is not intended to be used by the general audience of your Drupal site. Features provides tools for accomplishing two important tasks:

Task 1: Export features

You can build features in Drupal by using site building tools that are supported (see a short list under the Compatibility section).

Once you've built and configured functionality on a site, you can export it into a feature module by using the feature create page at admin/build/features/create.

Task 2: Manage features

The features module also provides a way to manage features through a more targeted interface than admin/build/modules. The interface at admin/build/features shows you only feature modules, and will also inform you if any of their components have been overridden. If this is the case, you can also re-create features to bring the module code up to date with any changes that have occurred in the database.

Including custom code and adding to your feature

Once you've exported your feature you will see that you have several files:

myfeature.info myfeature.module myfeature.[*].inc

You can add custom code (e.g. custom hook implementations, other functionality, etc.) to your feature in myfeature.module as you would with any other module. Do not change or add to any of the features .inc files unless you know what you are doing. These files are written to by features on updates so any custom changes may be overwritten.

Using Features to manage development

Because Features provides a centralized way to manage exportable components and write them to code it can be used during development in conjunction with a version control like SVN or git as a way to manage changes between development, staging and production sites. An example workflow for a developer using Features is to:

Make configuration changes to a feature on her local development site.
Update her local feature codebase using drush features-update.
Commit those changes using svn commit.
Roll out her changes to the development site codebase by running svn update on the server. Other collaborating developers can also get her changes with
svn update.
Reverting any configuration on the staging site to match the updated codebase by running drush features-revert.
Rinse, repeat.

Features also provides integration with the Diff module if enabled to show differences between configuration in the database and that in code. For site builders interested in using Features for development, enabling the diff module and reading API.txt for more details on the inner workings of Features is highly recommended.

Drush usage

Features provides several useful drush commands:

drush features
List all the available features on your site and their status.
drush features-export [feature name] [component list]
Write a new feature in code containing the components listed.
drush features-update [feature name]
Update the code of an existing feature to include any overrides/changes in your database (e.g. a new view).
drush features-revert [feature name]
Revert the components of a feature in your site's database to the state described in your feature module's defaults.
drush features-diff [feature name]
Show a diff between a feature's database components and those in code. Requires the Diff module.