WDI Darth Vader

Ruby

ERB (Embedded Ruby) Basics

Imagine that we have a route that supplies us some information. In our route, we can declare a few variables for use in an ERB page. We then call the ERB method to load a view. For example:

get '/darth_vader' do

    # let's have some variables
    name = 'Darth Vader'
    force_power = 'Force Choke'
    lightsaber_colour = 'red'

    # load a view using ERB
    erb :darth_vader

end

When this route is called, /views/darth_vader.erb will be rendered. The ERB file looks like the following:

<h1><%= name %></h1>

<p><%= name %> uses his <%= force_power %> to get his job done. He rocks a <%= lightsaber_colour %> lightsaber.</p>

This would render out to...

<h1>Darth Vader</h1>

<p>Darth Vader uses his force choke to get his job done. He rocks a red lightsaber.</p>

Rendering Content vs Executing Ruby Code

To Render content, we use the <%= %> tag. Inside of it, we can place variable names that are declared in our route (or class).

To Execute ruby code, we use the <% %> tag. Notice the lack of the = sign.

Loops in ERB

Now, imagine we have just fetched a list of Subordinants using ActiveRecord in a route. Each one has two attributes: name and rank.

get '/subordinates' do

    # load all the subordinates from the Subordinates table
    subordinates = Subordinates.all

    erb :subordinates

end

To render them, we'd want to conceptually just loop through them and put them somewhere. In command line ruby this would look like:

subordinates.each do |minion|
    puts minion.name + ' has a rank of ' + minion.rank
end

Our ERB view will look like that, but uses the executing ERB tag to run Ruby code. It also uses the Render tag as well... but only when we want to render content.

<h1>Subordinates</h1>

<% subordinates.each do |minion| %>

    <li>
    <%= minion.name %> has a rank of <%= minion.rank %>
    </li>

<% end %>