具有动态ID验证的Codeigniter表单字段

Question

How can i validate fields with names like this

<select name="mechanic_134" id="mechanic-134" class="form-control selectpicker">

mechanic_ is the general field name & 134 is a id i am getting from database. there are more fields to come like mechanic_135........mechanic_150.

i want to know how can i validate this field with dynamic id. please show it in code level. how it is done in controller & how the error output in view

Have a look (view)

http://www.screencast.com/t/jhXvVBUH

i have tried this in my controller but i don't know how to show this in view (the error message)

foreach ($this->input->post() as $key=>$value) {
  if (! strpos('mechanic_',$key) === FALSE ) {
    $this->form_validation->set_rules($key, 'Mechanic', 'trim|required');
  }
}

Thanks.