Is there a way to get a collection of all the Models in your Rails app?

Question

Is there a way that you can get a collection of all of the Models in your Rails app?

Basically, can I do the likes of: -

Models.each do |model|
  puts model.class.name
end

Thanks in advance.

Answer 1

Models do not register themselves to a master object, so no, Rails does not have the list of models.

But you could still look in the content of the models directory of your application...

Dir.foreach("#{RAILS_ROOT}/app/models") do |model_path|
  # ...
end

EDIT: Another (wild) idea would be to use Ruby reflection to seach for every classes that extends ActiveRecord::Base. Don't know how you can list all the classes though...

EDIT: Just for fun, I found a way to list all classes

Module.constants.select { |c| (eval c).is_a? Class }

EDIT: Finally succeeded in listing all models without looking at directories

Module.constants.select do |constant_name|
  constant = eval constant_name
  if not constant.nil? and constant.is_a? Class and constant.superclass == ActiveRecord::Base
    constant
  end
end

If you want to handle derived class too, then you will need to test the whole superclass chain. I did it by adding a method to the Class class:

class Class
  def extend?(klass)
    not superclass.nil? and ( superclass == klass or superclass.extend? klass )
  end
end

def models 
  Module.constants.select do |constant_name|
    constant = eval constant_name
    if not constant.nil? and constant.is_a? Class and constant.extend? ActiveRecord::Base
    constant
    end
  end
end

Answer 2

This seems to work for me:

  Dir.glob(RAILS_ROOT + '/app/models/*.rb').each { |file| require file }
  @models = Object.subclasses_of(ActiveRecord::Base)

Rails only loads models when they are used, so the Dir.glob line "requires" all the files in the models directory.

Once you have the models in an array, you can do what you were thinking (e.g. in view code):

<% @models.each do |v| %>
  <li><%= h v.to_s %></li>
<% end %>

Answer 3

Just in case anyone stumbles on this one, I've got another solution, not relying on dir reading or extending the Class class...

ActiveRecord::Base.send :subclasses

This will return an array of classes. So you can then do

ActiveRecord::Base.send(:subclasses).each do |model|
  puts model.name
end

Answer 4

Is there a way to find out which migration you're on from the console / application?

Answer 5

On one line: Dir['app/models/*.rb'].map {|f| File.basename(f, '.*').camelize.constantize }

:-)