# I already have users and students.
# I want to make an association between users and students.
# Both have a column ("codigo") which have values for the ones that should be associated.
# I have the following:

users = User.all
students = Student.all
users.each do |user|
  students.each do |student|
    if user.codigo == student.codigo
      user << student
    end
  end
end


# bitsweat provided me with this piece of code yesterday but I keep getting this:
# Student(#17477390) expected, got NilClass(#117210)

    users = User.all
    students = Student.all
    by_codigo = students.group_by(&:codigo)
    users.each do |u|
      u.students << by_codigo[u.codigo]
    end