Why does #triggering_element pick the wrong element?

Question

I'm triggering an ajax-enabled button on a form but Drupal's setting $form_state['#triggering_element'] to the wrong element.

The button is a child of a #tree and is identical to other buttons in other tree-ed structures, except for its parents. But I thought this was the point of #tree.

Looking at the drupal code in form.inc it's clear that Drupal only goes on the #name property to identify the triggering element, which is automatically set to 'op' for buttons. This seems to have no idea about trees or the element's parents.

The rather scant and very old docs for tree state:

#parents is used to create the name/ID of the form element itself.

But my button element's names are not being set to anything other than 'op'. I'm creating the buttons in a #process function for the parent element.

Example code

$form['group1'] = [
  '#prefix' => '<div>group1',
  '#suffix' => '</div>',
  '#tree' => TRUE,
  'trig' => [
    '#type' => 'submit',
    '#value' => 'ajax go',
    '#ajax' => [
      'callback' => 'mymod_ajax_callback',
      'wrapper' => 'foo',
      ],
  // Other elements part of group 1...
  ],
$form['group2'] = // The same.

A work-around is to code creating unique names for every one of these elements, but I feel I might be missing a trick/nuance?

Answer 1

The problem is in form_builder() where it fallbacks to the first button if no button can be found.

A comment from form_builder():

// Therefore, to be as consistent as we
// can be across browsers, if no 'triggering_element' has been identified
// yet, default it to the first button.
if (!$form_state['programmed'] && !isset($form_state['triggering_element']) && !empty($form_state['buttons'])) {
  $form_state['triggering_element'] = $form_state['buttons'][0];
}

More info can be found here: https://www.drupal.org/node/2546700#comment-11164091

There is also a patch for this problem that can be found in the link above.

Answer 2

First of all: you should implement all your $form modifications inside the form builder (hook_form or hook_form_alter), not inside ajax callbacks. And my mistake in one form was that when I have added few buttons with one ajax callback but set name html attribute using #attributes['name']. Drupal way in this case is to use '#name' parameter. Only when you set name attribute this way, $form_state['triggering_element'] and $form_state['clicked_button'] will be set to the correct element

Answer 3

To get a triggering element you must provide a unique '#name' for each button. Additionally, you can specify parameters to identify the action and record

function example_form($form, &$form_state){
    $form['groups'] = array(
        '#tree' => TRUE,
    );

    foreach(array(5,4,8,10) AS $id){

        $form['groups'][$id] = array(
            'id' => array(
                '#markup' => 'Group '. $id,
            ),
            // Some buttons with different actions for every group
            'btn_clone' => array(
                '#type' => 'submit',
                '#value' => 'Clone',
                // Any unique name for each button
                '#name' => 'clone-'. $id, 
                // Your additional data to identify the action
                '#my_op' => 'clone', 
                '#my_key' => $id,
            ),
            'btn_delene' => array(
                '#type' => 'submit',
                '#value' => 'Delete',
                // 
                '#name' => 'del-'. $id,
                '#my_op' => 'delete', 
                '#my_key' => $id,
            ),
        );  

    }
    return $form;
}

function example_form_submit($form, &$form_state){
    $clicked_element = drupal_array_get_nested_value($form, $form_state['triggering_element']['#parents']);
    drupal_set_message($clicked_element['#my_op'] .' '. $clicked_element['#my_key']);
}

Answer 4

Your example code isn't right, it should be:

$form['group1'] = array(
  '#prefix' => '<div>group1',
  '#suffix' => '</div>',
  '#tree' => TRUE,
);

$form['group1']['trig'] = array(
  '#type' => 'submit',
  '#value' => 'ajax go',
  '#ajax' => array(
    'callback' => 'mymod_ajax_callback',
    'wrapper' => 'foo',
  ),
);

You shouldn't need to use $form_state['#triggering_element'] as you should be able to do everything you need in the mymod_ajax_callback function

Answer 5

When you click on a submit input field, the browser sends the value of the submit button along with the fields. So giving you have a input like this in the HTML:

<input type="submit" value="foo" />

Foo will be posted along with which ever input/select/textarea elements are located in the form.

Drupal uses this to figure out which form element was pushed. The limitation of this is that if you have multiple inputs that have the same value, Drupal can't discern which of them was actually pushed (since it only can look at the data posted) so it will take the same one.

The only way to make Drupal able to figure out which input was clicked is to

• Give them different names
• Use ajax with different callback functions.
• Use some JS + hidden field to post the info and handle this yourself.

As you can see, if you want a solution that doesn't rely in JS, you need to have different values on the submit buttons.