A Simple CMS in Sinatra, Part II

In part one we installed MongoDB and used Mongoid to create some pages for our Simple CMS. We also built a web front-end for adding and viewing pages. In this tutorial, we’re going to add the other two CRUD operations that will allow users to edit and delete pages. Before we add the functionality, let’s add a couple of buttons to each page to allow you to edit or delete the page. Edit the show.slim file so that it looks like the following:

a href="/pages/#{@page.id}/edit" Edit this page,
  a href="/pages/delete/#{@page.id}" Delete this page

Editing Pages

We need to create a route handler for when the user clicks on the edit page URL. Add the following to main.rb (but make sure that it goes before the ‘/pages/:id’ route):

get '/pages/:id/edit' do
    @page = Page.find(params[:id])
    slim :edit
  end

This finds the page that is to be edited in the database using the id provided in the URL and stores it in an instance variable called @page. This will be accessible in the view, which is called edit.slim. We need to create that, so let’s do that now. Save the following as edit.slim in the views directory:

h1 Edit Page
  form action="/pages/#{@page.id}" method="POST"
    input type="hidden" name="_method" value="PUT"
    fieldset
      legend Edit page
      == slim :form
    input type="submit" value="Update"

Notice that this reuses the form partial that we used for the new page in the last tutorial. This keeps things consistent and keeps our code DRY. The form refers to values in the @page object, so some of the fields should be filled in with their current values. The form also has a hidden field that is used to tell Sinatra that the request is a PUT request. This is because most browsers don’t natively support any HTTP verbs other than GET and POST. The solution is to use Sinatra’s method override so that the request will be routed as if it was a PUT request. We are using a PUT request in this case because we are updating the resource. Next, we need to deal with what happens when the form is submitted. We need another route handler to deal with that, so add the following to main.rb:

put '/pages/:id' do
    page = Page.find(params[:id])
    page.update_attributes(params[:page])
    redirect to("/pages/#{page.id}")
  end

This finds the page that needs to be updated and updates it using Mongoid’s update_attributes method. It then redirects the user to the newly udpated page.

Deleting Pages

To delete a page, we are going to create a two-step process. First, we display a confirmation page to check that the user wishes to delete the page. Here is the route handler for that page:

get '/pages/delete/:id' do
    @page = Page.find(params[:id])
    slim :delete
  end

This route handler simply finds the page that is to be deleted and then shows a confirmation page. We need to create a view for this page, saved as delete.slim in the views directory:

h1 Delete Page
  p Are you sure you want to delete the page called #{@page.title}?
  form action="/pages/#{@page.id}" method="POST"
    input type="hidden" name="_method" value="DELETE"
    input type="submit" value="Delete"
  a href="/pages" cancel

We have to use a form to do this, as we will be using the DELETE HTTP method in our route handler that will delete the page. If we use a link then we can only use GET methods. We also need to use a hidden input field once again to use Sinatra’s method override, this time telling it to route the request as a DELETE method. All that is left to do is add a route handler at the bottom of main.rb to deal with that request:

delete '/pages/:id' do
      Page.find(params[:id]).destroy
      redirect to('/pages')
    end

This simply finds the page and uses the destroy method to remove it from the database. It then redirects to the page index.

Permalinks

So far we have been using the id of the Page object as a URL. MongoDB uses very big ids, so this means we have URLS such as /pages/5173f443a39401776a000001. These are very long, and not very descriptive, so it would be nice if we could create a ‘pretty URL’ based on the title of the page. To do this we have to add a new field to our Page model called permalink. This can be done with the following line of code:

field :permalink, type: String, default: -> { make_permalink }

This is not going to be a field that is filled in by the user in a form. It will be automatically created based on the title. We do this by using adding a default value that is set with a lambda that refers to a method called make_permalink. This method takes the title of the page and removes any spaces or punctuation with a hyphen (‘-‘) using various string methods. Here is the method, it just needs to go inside the Page class:

def make_permalink
    title.downcase.gsub(/W/,'-').squeeze('-').chomp('-') if title
  end

We can test this functionality in IRB using the following lines of code:

$> irb
  2.0.0-p0 :001 > require './main'
   => true

Now, search for the first document in our collection and you’ll find, amazingly, it already has a permalink field with an appropriate value:

2.0.0-p0 :002 > Page.first
  => #This is our first page

", permalink: "hello-world">

Welcome to the world of schemaless databases! Unfortunately, things are not as good as we first thought because if we try to query based on this field, we get an error:

2.0.0p0 :003 > Page.find_by(permalink: "hello-world")
  Mongoid::Errors::DocumentNotFound:

This is because the Page object with its new permalink field needs to be saved. This is easily done using the following code:

2.0.0p0 :004 > Page.first.save
   => true

Now we should be able to find the page using it’s permalink:

2.0.0p0 :005 > Page.find_by(permalink: "hello-world")
   => #This is our first page

", permalink: "hello-world">

Great! This means that every page created so far just needs to be saved to get it’s own permalink. If you have lots of pages, you can do this in one hit with the following line of code:

2.0.0p0 :007 > Page.all.each{|page| page.save }

Everything seems to be working as it should. Now we just need to create the route handler for pretty URLS. These will simply be the permalink and won’t start with /pages. For example, going to http://localhost:4567/hello-world will show the page with the title of “Hello World!”. This route handler will actually match every route, so to allow other routes to get through we will use Sinatra’s pass method in a resuce block which will be invoked if the page cannot be found in the database. Add the following code to main.rb:

get '/:permalink' do
    begin
      @page = Page.find_by(permalink: params[:permalink])
    rescue
      pass
    end
    slim :show
  end

This route handler will try to find the page based on the permalink given in the URL and store it in the @page instance variable before displaying the page using the show view that we have already created. If it can’t find the page in the database, then an error is thrown. The rescue method catches the error and calls the pass method, so Sinatra will simply move along to the next route to see if it matches.

Adding Some Style

Everything is working just as we want, but it all looks a bit nasty. Sinatra makes it really easy to use Sass to put together some nice stylesheets. All you need to do is add the following route handler to main.rb:

get('/styles/main.css'){ scss :styles }

Then place the following line in your layout file:

link rel="stylesheet" href="/styles/main.css"

Then create a file called styles.scss and save it in the views directory. This is where you put all of your styles. Here is one I knocked together. It adds a bit of color, makes the form a bit nicer and makes some of the links and submit input fields look like buttons:

$blue: #0166FF;

  body{
    margin: 0;
    padding: 0;
    font: 13px/1.2 helvetica, arial, sans-serif;
  }

  h1,h2,h3,h4,h5,h6{
    color: $blue;
  }

  .logo {
    background: #444;
    margin: 0;
    padding: 20px 10px;
    font-size: 44px;
    a,a:visited{ color: $blue; text-decoration: none;}
  }

  .button{
    border: none;
    border-radius: 8px;
    padding: 8px 12px;
    margin: 4px;
    color: #fff;
    background: $blue;
    text-decoration: none;
    font-weight: bold;
    display: inline-block;
    width: auto;
    &:hover{
      background: darken($blue,20%);
    }
  }

  label{
    display: block;
    font-weight: bold;
    font-size: 16px;
  }

  form, input, textarea{
    width: 100%;
  }

  input, textarea {
    border: #ccc 1px solid;
    padding: 10px 5px;
    font-size: 16px;
  }

Note for some of these styles to work, you will need to add a class of button to the relevant elements in your views. For example, show.slim now looks like this:

h1= @page.title
  - if @page.content
    == markdown @page.content

  a.button href="/pages/#{@page.id}/edit" Edit
  a.button href="/pages/delete/#{@page.id}" Delete

… and it looks a lot better for it!

That’s All Folks!

Now we have a fully functioning, albeit very simple, content management system. You can create, update, view and delete pages and they also have some pretty URLs based on their title. In the next part we’re going to create an admin section, flash messages, cache pages, versioning and timestamps. Please post in the comments any other features you’d like to see in the future.

Frequently Asked Questions about Building a Simple CMS in Sinatra