Question

In a rails application, I have a number of attributes for a model called Record. I want to design a method that when called on an attribute, returns the name of the attribute (which is essentially a method on the Record object). This name is then passed to an Hash, which returns a number (for the sake of this example, say the number is a percentage which is then multiplied by the original attribute value to get a new value).

For example, say my Record has four attributes: teachers, students, principals, and parents. The method would then look like the following:

def name
  **something here**
end

and the corresponding new_value method and PRECENTAGE hash would look like this:

def new_value
  self * PERCENTAGE[self.name]
end

PERCENTAGE = {
  "teachers"   => 0.40,
  "students"   => 0.53,
  "principals" => 0.21,
  "parents"    => 0.87
}

Then, to execute this whole thing, I would do Record.students.new_value, which would return new number of students according to the percentage obtained in the hash.

I know that to get the name of a method that is currently executing, you can do something like this: (found on http://ryat.la/7RDk)

def this_method
  __method__
end

but that won’t work for me, because I need the name of the previously executed method.

If you have any suggestions as to an alternative approach to accomplishing my goal, I’d be happy to try something else.

Answer 1

Ryan, I’m struggling to understand your question, but I think this is what you want, for record.teachers_percent, for example:

["teachers", "students", "principals", "parents"].each do |attrib|
  Record.class_eval <<-RUBY
    def #{attrib}_percent
      #{attrib} * PERCENTAGE[#{attrib.inspect}]
    end
  RUBY
end

Although this is probably a cleaner solution, giving record.percent(:teachers) or record.percent("teachers"):

class Record
  def percent(attrib)
    self.send(attrib) * PERCENTAGE[attrib.to_s]
  end
end