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Cambium serves three main purposes in Ruby on Rails applications:

  1. Bootstrap Rails' standard installation by performing additional setup (things I find myself doing at the beginning of every project).
  2. Facilitate development throughout the life of any project by abstracting repeatable bits of code.
  3. Provide a simple, but flexible CMS for those applications that require it.

For now, the documentation will be continued in the README. This will be moved out over time.

App Setup

Cambium lets you get up and running real fast. First, start you rails project as you normally would.

$ rails new my_app -d postgresql

Note: Cambium only supports PostgreSQL. If you need to use another database, I suggest you add an option into Cambium and create a pull request. However, I strongly encourage you to give PostgreSQL a try.

Add Cambium to your Gemfile.

gem 'cambium', '>= 1.0.0'

I would probably commit at this time (so it's easy to rollback if you don't like something Cambium did).

Generate Cambium's (simple) configuration file.

$ bundle exec rails g cambium:install

Edit the config (config/initializers/cambium.rb) to your liking.

Then, get your PostgreSQL database configured by editing config/database.yml to your appropriate settings.

Make sure you do not commit between this step and finishing the setup process. Cambium will ignore this database.yml file, which is good, as it may contain sensitive data.

Then, create your database:

$ bundle exec rake db:create

Although optional, I suggest you at least start with the default Gemfile.

$ bundle exec rails g cambium:gemfile

Remove the gems you don't want and then bundle.

$ bundle install

And now you can run Cambium's auto-setup generator.

$ bundle exec rails g cambium:app

When you're done, you can migrate (and annotate), and be on your way!

$ bundle exec rake db:migrate
$ bundle exec annotate

Admin / CMS

Install CMS

If you want to also setup a CMS, it's as simple as running the generator.

$ bundle exec rails g cambium:admin

Run the migrations Cambium created with the admin generator.

$ bundle exec rake db:migrate
$ bundle exec annotate

Make sure Cambium's engine is mounted in your config/routes.rb file.

mount Cambium::Engine => '/'

It's best to mount it at the root because Cambium automatically namespaces its routes.

At this point, you should be able to go to localhost:3000/admin and be redirected to the login page (if you are not signed in). Once you have an admin user and sign in successfully, you will be redirected to the admin dashboard.

Default Features

When you run the generators, you will get a handful of features by default. Cambium now ships with users, pages, media, and settings. Of these four, users is the only model that will be inserted directly in your app. Cambium handles the others.

See below for configuration and for adding users, while the following sections talk about how pages, media, and settings work.

Adding Users

We have a generator for creating a new user, which takes an --admin option if you want the user to have admin access.

$ bundle exec rails g cambium:user [username] [password] [--admin / --no-admin]

Generating Admin Controllers

A big portion of Cambium's power lies in its ability to spin up feature-full CMS controllers and views in a snap.

Before you generate an admin controller, you need to make sure you have a working data model. It's best if the model already has the columns you know you're going to need (it's easy to add or remove later, but quicker if you have what you need at the beginning).

Then you can run the generator.

$ bundle exec rails g cambium:controller [model]

Be sure you are using the proper class name of the data model.

For example, if I have a Page model, this would be the command:

$ bundle exec rails g cambium:controller Page

Note: I'm working on making Cambium more powerful all the time. At the moment, it works best with simple form-type data.

The generator does a few things:

  • Uses the standard Rails generate to generate a template in the admin namespace (using the example, your file would be at app/controllers/admin/pages_controller.rb).
  • Adds a namespaced route to your routes file (config/routes.rb).
  • Adds the Cambium config file (at config/admin/pages.yml in this example).
  • Adds a generic sidebar item for your controller at config/admin/sidebar.yml.

See below for information on the sidebar and controller settings.

Sidebar Settings

The sidebar in Cambium is driven by your config/admin/sidebar.yml settings file. It's pretty semantic and simple.

The default sidebar is:

  label: Dashboard
  route: cambium.admin_dashboard
  icon: dashboard
  label: Users
  route: cambium.admin_users
  icon: users
  controllers: ['users']

The important thing to remember is you have to define a unique key for each item. For example, if you accidentally named users as dashboard, then only the last dashboard item gets rendered.

The options are:

  • label: Text within the sidebar link
  • route: Route to apply to the link (for custom settings, replace cambium with main_app)
  • icon: The name of the icon to use, pulled from IcoMoon's free set
  • controllers: An array of controllers which, if the current page is using one of the controllers, the sidebar item will be highlighted (with an active class)

Controller Settings

The controller settings are what drive the behavior of Cambium. And it's why, for simple models, you don't have to add any code to your controller and you don't need any views.

Each controller's settings file is named for that controller, and can be found in config/admin. For example, the users controller settings are at config/admin/users.yml.

Here is the default set for the users controller:

model: User
  title: Site Users
  scope: all
      heading: Email
      sortable: true
      display_method: email_address
    new: New User
  button: Export Users
      label: Name
      label: Email
    delete: Delete User
  new: &new
    title: New User
        type: string
        type: string
        readonly: true
        type: password
        type: password
    <<: *new
    title: Edit User

Every setting plays a role. Let's step through each one.

  • model: The name (with class case) of the model to be used for this controller
  • table:title: The title to show on the controller's index view.
  • table:scope: The scope method to run on the model. Most of the time this will be all, but maybe you need to order, limit, or filter your results. You need to do this through an ActiveRecord Scope
  • table:columns:[column]: Each column gets its own unique key, which distinguishes it from others
  • table:columns:[column]:heading: The label for the column in the data table.
  • table:columns:[column]:sortable: Makes the column heading a link that will sort the data based on that column. This means the column must be a column in the database.
  • table:columns:[column]:display_method: Provides ability to use an alias method for displaying the content. For example, you may store a state as a integer but want to return a status string for the table. You'd use state as the column and status as the display method.
  • table:buttons:new: Label for the "New" button. If you don't want a new button, remove this setting.
  • export: This section handles an export option for your data table. Remove it if you don't want to offer that.
  • export:button: The label for the export button.
  • export:columns:[column]: Each column in the exported file gets its own unique key, which distinguishes it from others
  • export:columns:[column]:label: The heading in the exported file for that column.
  • export:columns:[column]:output: An optional method you can pass to each object to help with display.
  • form: Settings for the form.
  • form:buttons:delete: Label for the delete button. If you remove delete entirely, then no delete button will exist (though you'd have to manually remove the route from your routes file).
  • form:[new/edit]: New is the defaut, and most of the time Edit will inherit from new (the <<: *new is what handles that). But you can optionally override new values for your edit form.
  • form:[new/edit]:title: Title for the form page.
  • form:[new/edit]:fields:[field]: Each form field gets its own unique key to set it apart from the others.
  • form:[new/edit]:fields:[field]:type: The type of the HTML field to render, which uses SimpleForm. You can use heading here to break up your fields.
  • form:[new/edit]:fields:[field]:crop: If set to true, it will display a "Crop Image" option after a file has been uploaded. This only applies to file types.
  • form:[new/edit]:fields:[field]:readonly: If set to true, it will add the readonly attribute to the input field. Not supported for markdown fields.

Note: Aside from the usual form field types, Cambium uses Mark It Zero! to render markdown editors. You can pass markdown as the type option and it will give you a markdown editor.

A Note On Files

File fields use Dragonfly for uploading and processing. To add an upload field to the CMS, you need to have three attributes: _name, _uid, _gravity.

So, for example, if you have a field called, upload, You'll add the following to your database as string fields:

  • upload_name
  • upload_uid
  • upload_gravity

In addition to the features Dragonfly offers, Cambium has a built-in image cropper. The option for this will appear after a file has been uploaded if you specify the crop option for that field. If those conditions are present, you'll see a "Crop Image" below the image.

Overriding the Base Controller

I've rearranged Cambium's CMS controllers so there is a blank BaseController from which it inherits. You can manually override this in your app by creating a Cambium::BaseController and loading the appropriate files.

First, generate the controller.

$ bundle exec rails g controller cambium/base

That controller can inherit from any other controller in your app. The only thing you need to ensure is that it loads the CambiumHelper from the Cambium namespace. So, the base file should look like this:

class Cambium::BaseController < ApplicationController
  helper Cambium::CambiumHelper

You can change ApplicationController to any other controller in your application.


Cambium now ships with a flexible pages feature.

How Pages Work

Cambium keeps the base functionality of the pages within the gem in the Cambium::Page model. It provides a templating engine that enables you to add custom templates and apply them to individual pages.

The way it works is that you apply a template to an individual page. When that page is rendered, it will render the associated template file (minus the frontmatter, explained below) inside your application layout.

Working With Templates

To add a new template, just add a file to app/views/pages. The name of the file is what will drive the name of the template in the CMS.

To make everything work properly, it is recommended you keep the default form fields in your pages.yml config for the CMS.

Templates can have a set of custom fields that enable you to capture custom data on a page. You can't query that data directly, but you can get to it once you have a page. The configuration for each template uses YAML frontmatter, similar to how Middleman works.

Let's use an example to demonstrate. Let's say I have a Post model in my app and I want a listing of posts to be displayed on a News template. I would begin by creating a file for the news template: app/views/pages/news.html.erb.

Then let's say we want to capture a tagline attribute on the page. You would place the frontmatter at the top of your file, and it will look something like this:

title: News
    type: string
    label: Tagline

It's important in this case that you don't put the frontmatter in a ruby block (<% %>). It needs to be in plain text on the page.

Once this information is there, you are able to add a page with the News template in the CMS. Once you select the News template and save the page, the form will show the custom tagline field as an option. Go ahead and populate that field.

When you are creating the body of the template, it will all be based around the @page object. Meanwhile, the values of your fields are available as attribute on the @page object. So, if you wanted to display a listing of all the posts on this template, your file might look something like this:

title: News
    type: string
    label: Tagline

<h1><%= @page.title %></h1>
<h2><%= @page.tagline %></h2>

  <% Post.all.each do |post| %>
    <li><%= link_to post.title, post %></li>
  <% end %>

Setting Your Home Page

The page form has a Set as home page option on it. If you check this, that page will be designated as the home page of your application. To make it work, you'll have to amend your root call in config/routes.rb to load Cambium's home page.

root :to => 'cambium/pages#home'

If you don't have a page set as the home page, this will fail gracefully. If you have two pages set as the home page, it's going to pick the first match. In other words, setting a page as the home page doesn't unset all the other home pages.


There are a few methods on the Cambium::Page class:

  • home: The home page.
  • published: Published pages.
  • unpublished: Unpublished pages.

On an instance of a Cambium::Page, you can call the following methods:

  • template: A PageTemplate instance (see below for those options).
  • body: The body of the page (it's main block of content).
  • published?: Is the page published?
  • publish!: Publish the page.

There are also a few attributes on an instance of a Cambium::Page:

  • title
  • slug: Automatically generated from the title.
  • description
  • position
  • page_path: The full path to the page, including ancestors.
  • title_path: Combines all the titles of the ancestors, split by :.

The Cambium::PageTemplate class mainly focuses on the field values for a particular page, which it makes available as dynamic methods. But on the class itself, you have a few methods:

  • all: The templates in your app.
  • names: The names of all the templates in your app.
  • find: Takes a name argument and will return that template if it exists.

Adding Media

Cambium also ships with a media library by default. You can apply files from the library to an individual page. But, unlike other Cambium admin controllers, you won't use file as the field type. Instead it is a media field type which is specifically designed to pull files from the media library.

So, let's say you wanted to add a featured_image field to your News template. Your frontmatter may then look something like this:

title: News
    type: string
    label: Tagline
    type: media
    label: Featured Image

Accessing the actual file will work a little differently, though. We are using Dragonfly for handling uploads and processing, so you don't get the URL directly. Instead you get the Document object, which provides some flexibility on what you can do with it.

For example, if you just wanted the URL to the file itself, then you might add this to your template:

<%= @page.featured_image.upload.url %>

But what if you wanted it cropped on the fly? You could do something like this:

<%= @page.featured_image.upload.thumb('300x300#').url %>

Adding/Overriding Functionality

Cambium pages use the Cambium::Page model. If you want to add some additional functionality or change some inherent functionality, you could create a page model (app/models/page.rb) that inherits from Cambium::Page.

class Page < Cambium::Page
  # your custom configuration

You'll then need to override the controller and access the Page model instead of the Cambium::Page model. Place the following code in app/controllers/cambium/pages_controller.rb.

class Cambium::PagesController < ApplicationController
  def show
    slug = request.path.split('/').last
    @page = ::Page.find_by_slug(slug)
    render :inline => @page.template.content, :layout => 'application'

  def home
    @page = ::Page.home
    if @page.nil?
      render 'home_missing'
      render :inline => @page.template.content, :layout => 'application'

Disabling Pages

You can't technically disable pages, but you can hide its functionality. The best thing to do is to remove its configuration file (config/admin/pages.yml) and remove it from the sidebar config (config/admin/sidebar.yml).

Media Library

Cambium now ships with a media library. This lets you upload all your files to one main library. This feature especially will receive much more attention over time. Currently, they are built to be easily connected to pages.

To work with pages, see the previous section.

Cambium uses Dragonfly for uploading and image processing. To access a document directly, you will use the Cambium::Document model. Once you have a individual object, you can get to the Dragonfly methods through the upload attribute.

So, for example, you can get to the page of the file with document.upload.url, where document is a Cambium::Document object.


Here are the other methods on a document instance:

  • image?: Is the file an image?
  • pdf?: Is the file a PDF?
  • has_thumb?: Can we generate an image thumbnail for the file?
  • thumb_url: The URL to the thumbnail image (if it can be created).
  • ext: The file extension

Site Settings

Cambium also ships with site settings, which focuses on enabling your users to change setting through the UI.

You work with this like you would any other model, except it's more about finding individual records instead of creating custom fields for an object.

In other words, all the configuration happens in your config/admin/settings.yml file. You can see there are some default ones:

  type: string
  label: Site Title
  type: text
  label: Site Description

Any setting field you create you can access from the Cambium::Setting model. So, for example, if you want the value of site_title from the above config, you just query: Cambium::Setting.site_title.

Be warned, though, that if you need several settings on one page, you're better off grabbing a collection of the settings and then grabbing from your results as you need them. I'll leave that up to you!

Model Options

Cambium makes use of many gems, and uses the behavior of those gems to drive much of its power. In many cases, this requires added options to your model.

Searchable Models

To make items searchable (in the CMS and in the app), we use pg_search. You need to include the PgSearch module, and then call out the columns you want to search.

For example, if you have a Page model and you want title and body to be searchable, you're model might look like this:

class Page < ActiveRecord::Base
  include PgSearch
  multisearchable :against => [:title, :body]

Activity Log

If you want to track the history of a model's records (which also means adding it to the activity log in the CMS), you need to add has_paper_trail to your model.

class Page < ActiveRecord::Base

The activity log in particular makes use of the to_s method for the model. In this way, we make no assumptions about the default attribute that describes a model's record. Usually this is something like title or name. If it were title, then your model (from above) is:

class Page < ActiveRecord::Base

  def to_s

Markdown to HTML

As mentioned above, Cambium uses Mark It Zero! to render markdown editors. You, therefore, also have the option to store a markdown text attribute and have it automatically converted to HTML using the after_save callback.

If, for our Page example, you have body_markdown and body_html fields, you can add your body_markdown attribute to the form and then the following to your model:

class Page < ActiveRecord::Base
  converts_markdown :body_markdown, :body_html

See [this section]( html) of the Mark It Zero! docs for more information and options.


  1. Fork it ([my-github-username]/cambium/fork )
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create a new Pull Request