silverstripe-framework/docs/en/topics/module-development.md

Module Development

Introduction

Creating a module is a good way to re-use abstract code and templates across multiple projects. SilverStripe already has certain modules included, for example "framework" and "cms". These two modules are the core functionality and templates for any initial installation.

If you want to add generic functionality that isn't specific to your project, like a forum, an ecommerce package or a blog you can do it like this:

1. Create another directory at the root level (same level as "framework" and "cms"). This will contain all your module files.
2. The module directory must contain a _config sub-directory, or a _config.php file to be recognised.
3. Inside your module directory, follow our directory structure guidelines

Once this is done, SilverStripe will automatically include any PHP classes and templates from within your module.

Tips

Try to keep your module as generic as possible - for example if you're making a forum module, your members section shouldn't contain fields like 'Games You Play' or 'Your LiveJournal Name' - if people want to add these fields they can sub-class your class, or extend the fields on to it.

If you're using [api:Requirements] to include generic support files for your project like CSS or Javascript, and want to override these files to be more specific in your project, the following code is an example of how to do so using the init() function on your module controller classes:

:::php
class Forum_Controller extends Page_Controller {

   public function init() {
      if(Director::fileExists(project() . "/css/forum.css")) {
         Requirements::css(project() . "/css/forum.css");
      } else {
         Requirements::css("forum/css/forum.css");
      }
      parent::init();	
   }

}

This will use <projectname>/css/forum.css if it exists, otherwise it falls back to using forum/css/forum.css.

Conventions

Configuration

SilverStripe has a comprehensive Configuration system built on YAML which allows developers to set configuration values in core classes.

If your module allows developers to customize specific values (for example API key values) use the existing configuration system for your data.

:::php
// use this in your module code
$varible = Config::inst()->get('ModuleName', 'SomeValue');

Then developers can set that value in their own configuration file. As a module author, you can set the default configuration values.

// yourmodule/_config/module.yml
---
Name: modulename
---
ModuleName:
  SomeValue: 10

But by using the Config system, developers can alter the value for their application without editing your code.

// mysite/_config/module_customizations.yml
---
Name: modulecustomizations
After: "#modulename"
---
ModuleName:
  SomeValue: 10

If you want to make the configuration value user editable in the backend CMS, provide an extension to SiteConfig.

Publication

If you wish to submit your module to our public directory, you take responsibility for a certain level of code quality, adherence to conventions, writing documentation, and releasing updates. See contributing. All modules should be published on addons.silverstripe.org to make them discoverable by others.

Composer and Packagist

SilverStripe uses Composer to manage module releases and dependencies between modules. If you plan on releasing your module to the public, ensure that you provide a composer.json file in the root of your module containing the meta-data about your module.

For more information about what your composer.json file should include, consult the Composer Documentation.

A basic usage of a module for 3.1 that requires the CMS would look similar to this:

{
  "name": "your-vendor-name/module-name",
  "description": "One-liner describing your module",
  "type": "silverstripe-module",
  "homepage": "http://github.com/your-vendor-name/module-name",
  "keywords": ["silverstripe", "some-tag", "some-other-tag"],
  "license": "BSD-3-Clause",
  "authors": [
    {"name": "Your Name","email": "your@email.com"}
  ],
  "support": {
    "issues": "http://github.com/your-vendor-name/module-name/issues"
  },
  "require": {
    "silverstripe/cms": "~3.1",
    "silverstripe/framework": "~3.1"
  },
  "extra": {
    "installer-name": "module-name",
    "screenshots": [
      "relative/path/screenshot1.png",
      "http://myhost.com/screenshot2.png"
    ]
  }
}

Once your module is released, submit it to Packagist to have the module accessible to developers. It'll automatically get picked up by addons.silverstripe.org.

Versioning

Over time you may have to release new versions of your module to continue to work with newer versions of SilverStripe. By using Composer, this is made easy for developers by allowing them to specify what version they want to use. Each version of your module should be a separate branch in your version control and each branch should have a composer.json file explicitly defining what versions of SilverStripe you support.

Say you have a module which supports SilverStripe 3.0. A new release of this module takes advantage of new features in SilverStripe 3.1. In this case, you would create a new branch for the 3.0 compatible codebase of your module. This allows you to continue fixing bugs on this older release branch.

As a convention, the master or trunk branch of your module should always work with the master branch of SilverStripe. Other branches should be created on your module as needed if they're required to support specific SilverStripe releases.

You can have an overlap in supported versions, e.g two branches in your module both support SilverStripe 3.1. In this case, you should explain the differences in your README.md file.

Here's some common values for your require section (see getcomposer.org for details):

• 3.0.*: Version 3.0, including 3.0.1, 3.0.2 etc, excluding 3.1
• ~3.0: Version 3.0 or higher, including 3.0.1 and 3.1 etc, excluding 4.0
• ~3.0,<3.2: Version 3.0 or higher, up until 3.2, which is excluded
• ~3.0,>3.0.4: Version 3.0 or higher, starting with 3.0.4

Reference

How To:

• How to customize the CMS Menu
• How to extend the CMS interface

Reference:

Provide custom functionality for the developer via:

• DataExtension
• SiteConfig
• Page types

Follow SilverStripe best practice:

• Partial Caching
• Injector

Useful Links

• Introduction to Composer
• Modules
• Directory structure guidelines
• Debugging methods
• URL Variable Tools - Lists a number of page options, rendering tools or special URL variables that you can use to debug your SilverStripe applications