meta.rb

class AbstractClass
  def initialize(attributes)
    attributes.each do |name, value|
      unless self.respond_to?("#{name}=")
        self.class.send(:attr_accessor, name)
      end
      self.send("#{name}=", value)
    end
  end
end

my_class = Class.new(AbstractClass)
  => #<Class:0x007fe185762960>
c = my_class.new(a: 1, b: 2)
  => #<#<Class:0x007fe185762960>:0x007fe1857698f0 @a=1, @b=2>
c2 = my_class.new(d: 1, e: 2)
  => #<#<Class:0x007fe185762960>:0x007fe185791e90 @d=1, @e=2>
c2.a
  => nil