def reference_for_path(absolute_path)
      absolute_pathname = Pathname.new(absolute_path)

      unless absolute_pathname.absolute?
        raise ArgumentError, "Paths must be absolute #{absolute_path}"
      end

      objects.find do |child|
        child.isa == 'PBXFileReference' && child.real_path == absolute_pathname
      end
    end
def reference_for_path(absolute_path)
      absolute_pathname = Pathname.new(absolute_path)

      unless absolute_pathname.absolute?
        raise ArgumentError, "Paths must be absolute #{absolute_path}"
      end

      objects.find do |child|
        child.isa == 'PBXFileReference' && child.real_path == absolute_pathname
      end
    end
Returns the file reference for the given absolute path.

 @param  [#to_s] absolute_path
         The absolute path of the file whose reference is needed.

 @return [PBXFileReference] The file reference.
 @return [Nil] If no file reference could be found.