[SOLVED] D7/Views Small module to turn text field to dropdown list when exposed.

Hi,

You need to implement hook_form_alter in your module to alter your views exposed form. It will change the textfield to select list and set options fetched from the database.

thanks for that, needed it for another entity type but easily changed it.

Thanks for sharing! (I wrote it if anyone has questions about it)

When you need to have grouped-by values (duplicates filtered) you may use this function instead:

function dd_city_form_views_exposed_form_alter(&$form, &$form_state) {
  $field_id = 'field_whatever';

  // Only alter forms with the necessary field
  if (isset($form[$field_id .'_value'])) {    
    // Build a query to get grouped by values of the field
    $query = db_select('field_data_' . $field_id, 'fd');
    $query->addField('fd', $field_id . '_value', 'field');
    $query->groupBy($field_id . '_value');

    // Execute query
    try {
      $result = $query->execute();
    }
    catch (Exception $e) {
      // Error handling: Just a message and no change of the field
      drupal_set_message(t('SQL Query failed when rewriting field %field from TEXT field to SELECT field.', array('%field' => $field_id)), 'warning');
      return;
    }
    
    // Start with a default so the filter is optional
    $options = array('' => t('any'));

    // Build the options array based on the grouped field values
    foreach($result as $row) {
      $options[$row->field] = $row->field;
    }
    
    // Alter the field
    $form[$field_id .'_value']['#type'] = 'select';
    $form[$field_id .'_value']['#options'] = $options;
    $form[$field_id .'_value']['#size'] = 1;
  }
}

function hook_form_views_exposed_form_alter(&$form, &$form_state){

if($form['#id']==){ // view exposed form id has been taken for putting up a condition
$result = db_select('node', 'n')
->distinct()
->fields('n',array('nid','title')) //nid & title as per my requirement, get your fields as per requirement
->condition('n.type', 'events','=')
->execute()
->fetchAll();
$data_variable=array(); //simple array variable to store the result data
$data_variable['select']="-Select-"; //to set a default value

foreach ($result as $key=> $val){
$data_variable[$val->title]=$val->title;
}

$form['
']=array( //you can put your form field machine name, which you want to convert to drop down list.
'#type' => 'select', // here changed the field type to select.
'#options' =>$data_variable, // and then passed the values stored in the data_variable
'#default_value' => 'select', //setting default value for the new drop down list
);
}
}

While changing a view exposed filter form field from text to select list the above code worked for me, also there was an observation, that if there is no default value entered in the text box then "An illegal choice has been detected. Please contact the site administrator." would appear.
So there has to be a default value in the text field. Now, the newly customized form field(drop down) also needs to have a default value.
That also has been mentioned in the above code.
Note: both the default values i;e in the text field and the drop down list, has be same.
In my case "select".
Hope this will help you.

I was able to turn a list of nodes into an exposed filter using the Views Reference Filter module.

If somebody wants to do this in Drupal 8 quick & dirty via theme hook:

THEMENAME.theme

function THEMENAME_form_alter(&$form, &$form_state, $form_id) {
  if ($form['#id'] == 'views-exposed-form-FORM-ID') {

    $nids = \Drupal::entityQuery('node')->condition('type','NODETYPE')->execute();
    $nodes = \Drupal\node\Entity\Node::loadMultiple($nids);
    $options = ['' => 'All'];

    foreach($nodes as $nid => $node) {
      $value = $node->get('field_FIELDNAME')->getString();

      if (isset($value)) {
        $options[$value] = $value;
      }
    }

    if (isset($form['FIELDNAME'])) {
      $form['FIELDNAME']['#type'] = 'select';
      $form['FIELDNAME']['#options'] = $options;
      $form['FIELDNAME']['#size'] = 1;
    }
  }
}