How to iterate instance variables within instance variables in view?

Question

I'm using Rails 3.2. I have the following code:

# transports_controller.rb
@transports = %w(car bike)

@transports.each do |transport|
  instance_variable_set("@#{transport.pluralize}", 
                        transport.classify.constantize.all)
end

# transports/index.html.erb
<% @transports.each do |transport| %>
  <h1><%= transport.pluralize.titleize %></h1>
  <% @transport.pluralize.each do |transport_item| %>
    <%= transport_item.name %><br>
  <% end %>
<% end %>

The controller code is correct, but the view code is wrong. @transport.pluralize.each cannot be called literally . Expected result is:

<h1>Cars</h1>
Ferrari<br>
Ford<br>

<h1>Bikes</h1>
Kawasaki<br>
Ducati<br>

How do I do this?

I get that you are not getting your expected result, but what are you getting? An error? Output is in the wrong order? Which call to @transport.pluralize is failing? Need a little more to go on here. — theIV
– theIV, Commented May 15, 2013 at 2:13
The @transport.pluralize cannot be called literally. I haven't tested this, but I'm sure that is not the way to write it. — Victor
– Victor, Commented May 15, 2013 at 2:23
Are you talking about in the loop? If so, just like you do instance_variable_set, there is an instance_variable_get. Is that what you're getting at? — theIV
– theIV, Commented May 15, 2013 at 2:26
Great great. That's what I wanted. Thanks for the tip. You can put that as an answer, then I will tick it, so that you get points. Thanks again. — Victor
– Victor, Commented May 15, 2013 at 2:28
glad that's what you were looking for. Submitted as an answer. Cheers. — theIV
– theIV, Commented May 15, 2013 at 2:30

theIV · Accepted Answer · 2013-05-15 02:30:31Z

1

Just like you use instance_variable_set, there is an instance_variable_get available.

answered May 15, 2013 at 2:30

theIV

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Stefan · Accepted Answer · 2013-05-15 07:45:48Z

1

You don't have to create instance variables for this, just use an array (or a hash):

transport_classes = [Car, Bike]

@transports = transport_classes.map { |transport_class|
  [transport_class, transport_class.all]
}
# this returns a nested array:
# [
#   [Car, [#<Car id:1>, #<Car id:2>]],
#   [Bike, [#<Bike id:1>, #<Bike id:2>]
# ]

In your view:

<% @transports.each do |transport_class, transport_items| %>
  <h1><%= transport_class.to_s.pluralize.titleize %></h1>
  <% transport_items.each do |transport_item| %>
    <%= transport_item.name %><br>
  <% end %>
<% end %>

answered May 15, 2013 at 7:45

Stefan

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