Question

I have a ruby code that currently look like this:

grades.sum{|g| g.grade * g.weight}

For a user maintained DSL, I would like to implement something like this:

grades.sum('grade' * 'weight')

Is this possible?

Answer 1

No, it’s not possible unless you monkeypatch the class String to add your application logic (please don’t do that). But this -which even looks beter- is possible if you play a little bit with instance_eval:

grades.sum { grade * weight }

For example, let’s assume grades is an array:

module Enumerable
  def sum(&block)
    inject(0) { |acc, x| acc + x.instance_eval(&block) }
  end
end