paperclip interpolator

paperclip_interpolator.rb

class PaperclipInterpolator
  def initialize pattern
    @pattern = pattern
    @methods = []
    @template = Paperclip::Interpolations::all.reverse.inject( pattern.dup ) do |result, tag|
      result.gsub(/:#{tag}/) do |match|
        @methods << tag.to_sym
        "%{#{tag}}"
      end
    end
    @methods.uniq!
  end
  def call attachment, style_name
    values = @methods.map{|method| [method, Paperclip::Interpolations.send(method, attachment, style_name)] }
    @template % Hash[values]
  end
  def interpolate pattern, attachment, style_name
    raise "Wrong interpolation pattern: expected '#{@pattern}' got '#{pattern}'" unless pattern == @pattern
    call(attachment, style_name)
  end

  def self.interpolate pattern, attachment, style_name
    @interpolators ||= {}
    @interpolators[pattern] ||= new(pattern)
    @interpolators[pattern].call(attachment, style_name)
  end
end