Slimmer provides Rack middleware for applying a standard header and footer around pages returned by a Ruby (Rack) application.
It does this by taking the page rendered by the application, extracting the contents of
div with id 'wrapper' and inserting that into a
div with the same id in one of its
templates. It also transfers various other details, such as
Use in a Rails app
Slimmer provides a Railtie so no configuration is necessary. By default it will use the Plek gem to look for the 'static' (previously 'assets') host for the current environment.
If you want to use your own set of templates you will need to specify the appropriate host eg.
YourApp::Application.configure do config.slimmer.asset_host = 'http://your.server.somewhere' end
it expects to find templates in a folder called 'templates' on that host.
Slimmer will work as standard rack middleware:
use Slimmer::App, :asset_host => "http://my.alternative.host"
Asset tag helpers
To get asset tag helpers to point to your external asset server, add
config.action_controller.asset_host = "http://my.alternative.host"
Specifying a template
A specific template can be requested by giving its name in the
X-Slimmer-Template HTTP header.
In a controller action, you can do this by calling
class MyController < ApplicationController def index slimmer_template 'homepage' end end
There's also a macro style method which will affect all actions:
class YourController < ApplicationController slimmer_template :admin end
To get this, include Slimmer::Template in your ApplicationController:
class ApplicationController < ActionController::Base include Slimmer::Template end
Slimmer can be configured with a logger by passing in a logger instance
(anything that quacks like an instance of
Logger). For example, to log
to the Rails log, put the following in an initializer:
YourApp::Application.configure do config.slimmer.logger = Rails.logger end
Note: This can't be in
application.rb because the Rails logger hasn't been initialized by then.
By default if you pass in a logger with its log level set to
debug, slimmer will dup this logger and reduce the level to
info. (Slimmer's debug logging is very noisy). To prevent this, set the
enable_debugging option to true. e.g. for Rails:
YourApp::Application.configure do config.slimmer.enable_debugging = true end
To use shared template components you need to include the shared template resolver
class ApplicationController < ActionController::Base include Slimmer::SharedTemplates end
This will make calls out to static when you try and render a partial prefixed with
<%= render partial: 'govuk-component/example_component' %>
You will need a copy of static running for the templates to be loaded from.
Testing shared components
In test mode (when
true), shared components are not
fetched from Static. Instead they are rendered as a dummy tag which contains a
JSON dump of the
locals - the arguments passed to the component.
A test helper is included which returns a CSS selector for finding a given component to assert that it was used. You can make it available in your tests with:
require 'slimmer/test_helpers/shared_templates' include Slimmer::TestHelpers::SharedTemplates
And then assert that the component has been used:
Or look for one of the arguments to the component which will have been
JSON.dumped inside the tag:
within(shared_component_selector('title')) do expect(page).to have_content(expected_title_text) end
Slimmer was extracted from a much larger project called 'skinner'. 'slimmer' referred to the size of its code compared to skinner (which also acted as an HTTP proxy and mixed in a few other concerns). Over time the codebase has grown a little, but the name stuck.