user_contoller.rb

def admission2
    @student = Student.find params[:id], :include => [:guardians]
    @guardian = Guardian.new params[:guardian]
    @g_u=GuardianUser.new()
    @g_u[:guardian_id]=@guardian[:id]
    @g_u[:email]=@guardian[:email]
    @g_u[:ward_id]=@guardian[:ward_id]
    randstr=""
    chars=("0".."9").to_a + ("a".."z").to_a + ("A".."Z").to_a
    8.times { randstr << chars[rand(chars.size -1)] }
    @g_u[:salt]=randstr
    @g_u[:hashed_password]=Digest::SHA1.hexdigest(@g_u[:salt]+@g_u[:email])
    if request.post? and @guardian.save and @g_u.save
      redirect_to :controller => "student", :action => "admission2", :id => @student.id
    end
  end
error
/var/www/admin/app/controllers/student_controller.rb:93:in `size'
/var/www/admin/app/controllers/student_controller.rb:93:in `admission2'
/var/www/admin/app/controllers/student_controller.rb:93:in `times'
/var/www/admin/app/controllers/student_controller.rb:93:in `admission2'

rand(chars.size - 1)