Deface

Deface is a library that allows you to customize ERB views in a Rails application without editing the underlying view.

It allows you to easily target html & erb elements as the hooks for customization using both CSS and XPath selectors as supported by Nokogiri.

Deface temporarily converts ERB files into a pseudo HTML markup that can be parsed and queired by Nokogiri, using the following approach:

<%= some ruby code %>

becomes 

<erb-loud> some ruby code </erb-loud>

and 

<% other ruby code %>

becomes

<erb-silent> other ruby code </erb-silent>

Deface overrides have full access to all variables accessible to the view being customized.

Deface::Override

A new instance of the Deface::Override class is initialized for each customization you wish to define. When initializing a new override you must supply only one Target, Action & Source parameter and any number of Optional parameters. Note, the source parameter is not required when the "remove" action is specified.

Target

  • :file_path - The relative file path of the template / partial where the override should take effect eg: "shared/_person", "admin/posts/new" this will apply to all controller actions that use the specified template.

  • :virtual_path - The controller and action name where the override should take effect eg: "controller/action" or "posts/index" will apply to all layouts, templates and partials that are used in the rendering of the specified action.

Action

  • :remove - Removes all elements that match the supplied selector

  • :replace - Replaces all elements that match the supplied selector

  • :insert_after - Inserts after all elements that match the supplied selector

  • :insert_before - Inserts before all elements that match the supplied selector

Source

  • :text - String containing markup

  • :partial - Relative path to a partial

  • :template - Relative path to a template

Optional

  • :name - Unique name for override so it can be identified and modified later. This needs to be unique within the same :virtual_path or :file_path

Examples

Replaces all instances of h1 in the posts/_form.html.erb partial with <h1>New Post</h1>

Deface::Override.new(:file_path => "posts/_form", :name => "example-1", :replace => "h1", :text => "<h1>New Post</h1>")

Inserts <%= link_to "List Comments", comments_url(post) %> before all instances of p with css class comment in any layout / template / partial used when rendering PostsController#index action:

Deface::Override.new(:virtual_path => "posts/index", :name => "example-2", :insert_before => "p.comment", :text => "<%= link_to "List Comments", comments_url(post) %>")

Inserts the contents of shared/_comment.html.erb after all instances of div with an id of comment_21 in any layout / template / partial used when rendering PostsController#show action:

Deface::Override.new(:virtual_path => "posts/show", :name => "example-3", :insert_after => "div#comment_21", :partial => "shared/comment")

Removes any instance of <%= helper_method %> in the `posts/new.html.erb" template:

Deface::Override.new(:file_path => "posts/new", :name => "example-4", :remove => "erb-loud:contains('helper_method')" )