shoulda: ensure_length_of.integer_field and associations with foreign key fields

We're still using Rails 2.3.X and therefore are stuck with thoughtbot-shoulda version 2.11.1 Which unfortunately doesn't come with a lot of the niceties of the most recent version. We've pulled some backports into our initializers directory to bring it up to speed - notably the ability to deal with foreign keys on association-definitions (see below).

But there's one small thing that has always annoyed me about shoulda - and isn't in any version.

That's the ability for ensure_length_of (the validates_length_of macro) to handle integer fields. Active Record can deal with it... therefore shoulda should too.

It's a tiny hack, but I'm currently too lazy to fork shoulda and write the tests to make it a viable pull-request, but here's a monkeypatch that'll get it working for you.

Save it into something like: config/initializers/shoulda_monkeypatches.rb, then use it like this:

   should ensure_length_of(:my_integer).integer_field.is_equal_to(4)

module Shoulda # :nodoc:
  module ActiveRecord
    module Matchers

      # I don't like it that ensure length of only works for strings.
      # This patch makes it also work for integers if we want
      class NewEnsureLengthOfMatcher < EnsureLengthOfMatcher
        def integer_field
          @integer_field = true
          self
        end      

        # re-write "string_of_length" to make the string an int-string
        def string_of_length(length)
          if @integer_field
            '1' * length # yep, this works for an int field
          else
            'x' * length
          end
        end
        
      end      
      # and override ensure_length_of to use our new class
      def ensure_length_of(attr)
        NewEnsureLengthOfMatcher.new(attr)
      end
    end
  end
end

Oh, and for the foreign-key backport:

module Shoulda # :nodoc:
  module Matchers
    module ActiveRecord
      # use the actual foreign key for an association
      class AssociationMatcher
        def foreign_key
          if foreign_key_reflection
            if foreign_key_reflection.respond_to?(:foreign_key)
              foreign_key_reflection.foreign_key.to_s
            else
              foreign_key_reflection.primary_key_name.to_s
            end
          end
        end      
      end      
    end
  end
end