Undrestanding yield and scopes

help.rb

# what should I do, that a() would run in context of class A, not give "block in <main>': undefined method `a' for main:Object (NoMethodError)"

class A
  def a
    puts "a"
  end
end


class B
  def b(&block)
    A.module_eval do
      yield
    end
  end
end


B.new.b do
  a()
end

instance_eval &block saved the day