User Roles with bit mask

bit_mask.rb

ROLES = %i(student mentor guardian admin td)

@roles_mask = nil

def set(roles)
  @roles_mask = (roles & ROLES).map { |r| 2**ROLES.index(r) }.inject(0, :+)
end

def get
  ROLES.reject do |r|
    ((@roles_mask.to_i || 0) & 2**ROLES.index(r)).zero?
  end
end

puts "setting roles"
set([:mentor, :admin])
puts @roles_mask.to_s(2)
puts "---"

puts "getting roles"
puts get