Question

I have a Skill model, which has many prerequisites (or prereqs in my model), and I need to create a map N-levels deep of the prerequisites for a skill, because I need to pass this information to Javascript (with the gon gem in my controller) for some crazy, HTML5/KineticJS action that shows the birds eye view of the relationship between this skill and others.

Right now, the code below is working great to consistently map 5 levels deep.

delegate :url_helpers, to: 'Rails.application.routes'

def prereqs_map
  prereqs_array = [ self.title.to_s, url_helpers.skill_path(self), Array.new(prereqs) ]
  prereqs_array[2] = prereqs_array[2].map do |prereq1|
    prereq1 = [ prereq1.title.to_s, url_helpers.skill_path(prereq1), Array.new(prereq1.prereqs).map do |prereq2|
      prereq2 = [ prereq2.title.to_s, url_helpers.skill_path(prereq2), Array.new(prereq2.prereqs).map do |prereq3|
        prereq3 = [ prereq3.title.to_s, url_helpers.skill_path(prereq3), Array.new(prereq3.prereqs).map do |prereq4|
          prereq4 = [ prereq4.title.to_s, url_helpers.skill_path(prereq4), Array.new(prereq4.prereqs).map do |prereq5|
            prereq5 = [ prereq5.title.to_s, url_helpers.skill_path(prereq5), [] ]
          end ] # prereq depth 5
        end ] # prereq depth 4
      end ] # prereq depth 3
    end ] # prereq depth 2
  end   # prereq depth 1

  return prereqs_array
end

The problem, as you can see, is it’s super messy with nested maps and there’s no way that I can figure out to pass a depth parameter and have the method map out to whatever depth I pass it.

I figure there has to be a better way of doing this. Any thoughts?

Answer 1

Try this:

class Skill
  # has many prereqs?

  def prereqs_map(depth = 5)
    mapping = Proc.new do |node, depth, current_level|
      [node.title.to_s, url_helpers.skill_path(node), node.prereqs.map {|prereq| mapping.call(prereq, depth, current_level+1)}] if current_level <= depth
    end
    mapping.call(self, depth, 0)
  end

end

>> skill.prereqs_map(5)