CODEWITHSUNDEEP
ruby-on-rails
Leahcim
Leahcim

Reputation: 42049

rendering two instance variables with one partial

In the index file of a Rails to-do app (code from Railscast), it lists out the incomplete and complete tasks that were assigned to instance variables in the tasks controller. Notice how it calls render @incomplete_tasks and render @complete_tasks, whereas the partial is only called 

_task.html.erb

It appears this one partial is used for rendering both incomplete and complete tasks. Is Rails able to ignore the first half of the instance variables (ie. @incomplete and @complete) to use the one partial for rendering both?

controller

 def index
    if current_user
      @incomplete_tasks = current_user.tasks.where(complete: false)
      @complete_tasks = current_user.tasks.where(complete: true)
    end
  end

Index

<% if @incomplete_tasks.empty? && @complete_tasks.empty? %>
    <p>Currently no tasks. Add one above.</p>
  <% else %>
    <h2>Incomplete Tasks</h2>
    <div class="tasks" id="incomplete_tasks">
      <%= render @incomplete_tasks %>
    </div>

    <h2>Complete Tasks</h2>
    <div class="tasks" id="complete_tasks">
      <%= render @complete_tasks %>
    </div>
  <% end %>

_task.html.erb

<%= form_for task, remote: true do |f| %>
  <%= f.check_box :complete %>
  <%= f.label :complete, task.name %>
  <%= link_to "(remove)", task, method: :delete, data: {confirm: "Are you sure?"}, remote: true %>
<% end %>

Upvotes: 1

Views: 422

Answers (3)

nikolayp
nikolayp

Reputation: 17949

There is full answer on this question.

http://guides.rubyonrails.org/layouts_and_rendering.html

2.2.13 Avoiding Double Render Errors

Upvotes: 0

Intrepidd
Intrepidd

Reputation: 20938

Copying the answer of @ryanb, see it here : Rails: Rendering Models?

If you pass a model directly to render it will attempt to render a partial for it.

<%= render @thing %>

That is the same as.

<%= render :partial => 'things/thing', :object => @thing %>

If you pass an array of models...

<%= render @things %>

It will render the _thing partial for each as if you did this.

<%= render :partial => 'things/thing', :collection => @things %>

Note: this requires Rails 2.3. If you have earlier versions of Rails you'll need to use the :partial option to do the same thing.

<%= render :partial => @thing %>

Upvotes: 0

wjandali
wjandali

Reputation: 112

So rails looks at the model objects to determine which partial to use when you use that kind of syntax. In both cases the instance variables contain tasks so rails knows to use the _task partial.

Upvotes: 2

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