Merb plugins are distributed as gems, which makes for easy versioning and management. Your merb plugin gems can be installed either on a per-application basis, or for an entire system. The following sections will outline how to get started with plugins.

Please note that this section assumes some knowledge of rubygems and the gem command-line tool.

Merb automatically attempts to use the “gems” directory of your application as a repository for application-specific gems. The command for installing gems accepts an optional argument which allows you to specify the installation directory for a given gem. To install plugins for a specific merb application, you can run the following command:

gem install -i path/to/my/app/gems merb-fixtures-0.9.5.gem

Once the gem is installed, you can follow the README file to determine what configuration changes are necessary. For example, if you've just installed the merb-fixtures plugin you might need to add the following to your config/init.rb:

dependency "merb-fixtures"

Note that if you intend to distribute a merb application that makes use of several plugins, it may be easier for other developers who wish to work on your code if you install the gems using this method. If you don't, they may have to go hunting for the dependencies themselves.

If you have several applications that you know will be making use of the same plugin, you might want to install it to your system's gem repository. Once installed to the system gem repository, this plugin will then be available to any merb application you install on the system.

gem install merb-fixtures-0.9.5.gem

Again, once the gem is installed you may need to make plugin-specific configuration changes to your merb application(s). Check the README file for your plugins.

Writing plugins for merb is dead simple

$ merb-gen plugin myplugin

Then there are two ways for build a merb plugin:

1. Build the plugin outside your merb app
2. Build the plugin inside your merb app

The second way, need some simple step.

do this:

$ mkdir /path/to/myapp/gems/development
$ mv myplugin /path/to/myapp/gems/development

Then in edit before_app_loads in your init.rb (/path/to/myapp/config/init.rb) like this:

Merb::BootLoader.before_app_loads do
  dev_gems = Dir.glob("#{Merb.root}/gems/development/**/lib/*.rb")
  dev_gems.each { |dev_gem| require dev_gem }
end

That's all!

Now you can live edit your all your plugins (which are really gems, remember) and test them inside your app.