How to modify account page adding possibility for a user to chose one of 2 roles

Question

I have Drupal 7 installed on my WAMP localhost. I need to add a widget to the account page to allow users to chose 1 of 2 roles (recruiter or applicant). Having chosen one role the user cannot switch back to the other again. For particular reasons I do not consider possibility to chose role DURING registration.

I have read and searched a lot on this subject recently but have not yet found the solution. I understand it can be done with the help of hook_form_alter() in a module? Then I need to update the users_roles table

Could you please guide me a bit through the code or tell me where I can find some examples.

Thank you.

---

Meanwhile I moved on - I have created the module with hook_form_alter(). The 2 radiobattons show up on non admin user's page (see attached screenshot).

The code is missing saving to the database and probably validation is also required - I dont know where to go yet. Looking forward to your comments/corrections of the below code which is far from being professional.

<?php
/*
 * Implements hook_form_alter().
 */
global $user;
if($user->uid !== 1) {  
function testpwd_form_alter(&$form, &$form_state, $form_id) {
#   krumo($form_id);

    switch ($form_id) {
        case 'user_profile_form' :

// Adding radiobuttons
            $form['account']['roles']['#type'] = 'radios'; 
            $form['account']['roles']['#title'] = 'Role';
            $form['account']['roles']['#weight'] = -20;
            $form['account']['roles']['#access'] = true; 
            $form['account']['roles']['#default_value'] = '';
            $form['account']['#access'] = true; /*without this Roles do not show up on autheticated 
            user's profile page. I think after setting it to TRUE access for the nested elements has also 
            changed to TRUE. I need to check what changed and set access to False for some nested elements.  */

            $form['account']['current_pass']['#access'] = false; /*see comment 1 line above. 
            Not needed on this page as for changing passwords users are directed to Master site 
            (2 sites joined with Bakery sso module).*/      

            $form['account']['roles']['#options'][115362423] = 'applicant';
            $form['account']['roles']['#options'][100482362] = 'recruiter';

//To hide Roles options appeared. Where hide() does not work I used unset() 
            unset($form['account']['roles']['#options'][30037204]); // admin
            hide($form['account']['roles'][2]); //auth users
            unset($form['account']['roles']['#options'][139881272]);
            unset($form['account']['roles']['#options'][29617163]); //content admin

            krumo($form);

//nice print of arrays
            echo '<pre>', print_r($form, true), '</pre>';
        break;

    }
  }
}

Answer 1

The drupal module Auto Assign Role allows you to do this (users can select during registration, not afterwards).

The module name is a little misleading because although one of its features is allowing for automatically assigning roles to users, another of its features is to allow users to select a role for themselves.