Rails: An elegant way to display a message when there are no elements in database

Question

I realized that I\'m writing a lot of code similar to this one:

<% unless @messages.blank? %>
  <% @messages.each do |message|  %>
    <%# cod         


        

Answer 1

You could split up your two cases into different templates: one if messages exist and one if no message exist. In the controller action (MessagesController#index probably), add as the last statement:

render :action => 'index_empty' if @messages.blank?

If there are no messages, it'll display app/views/messages/index_empty.html.erb. If there are messages, it'll fall through and display app/views/messages/index.html.erb as usual.

If you need this in more than just one action, you can nicely refactor it into a helper method like the following (untested):

def render_action_or_empty (collection, options = {})
    template = params[:template] || "#{params[:controller]}/#{params[:action]}"
    template << '_empty' if collection.blank?
    render options.reverse_merge { :template => template }
end

With this, you just need to put render_action_or_empty(@var) at the end of any controller action and it'll display either the 'action' template or the 'action_empty' template if your collection is empty. It should also be easy to make this work with partials instead of action templates.

Answer 2

Below solution works for me because I want tr and td with colspan property:

<%= render(@audit_logs) || content_tag(:tr, content_tag(:td, 'No records',colspan: "11"))%>

Answer 3

If you use the :collection parameter to render e.g. render :partial => 'message', :collection => @messages then the call to render will return nil if the collection is empty. This can then be incorporated into an || expression e.g.

<%= render(:partial => 'message', :collection => @messages) || 'You have no messages' %>

In case you haven't come across it before, render :collection renders a collection using the same partial for each element, making each element of @messages available through the local variable message as it builds up the complete response. You can also specify a divider to be rendered in between each element using :spacer_template => "message_divider"

Answer 4

As a note, you may as well just iterate over an empty array if you're looking for efficiency of expression:

<% @messages.each do |message|  %>
  <%# code or partial to dispaly the message %>
<% end %>
<% if (@messages.blank?) %>
  You have no messages.
<% end %>

While this does not handle @messages being nil, it should work for most situations. Introducing irregular extensions to what should be a routine view is probably complicating an otherwise simple thing.

What might be a better approach is to define a partial and a helper to render "empty" sections if these are reasonably complex:

<% render_each(:message) do |message|  %>
  <%# code or partial to dispaly the message %>
<% end %>

# common/empty/_messages.erb
You have no messages.

Where you might define this as:

def render_each(item, &block)
  plural = "#{item.to_s.pluralize}"
  items = instance_variable_get("@#{plural}")
  if (items.blank?)
    render(:partial => "common/empty/#{plural}")
  else
    items.each(&block)
  end
end