Using hook_node_submit() from a custom module

Question

I have built a custom module named 'ABC'. I have created a content type 'CT' having some text fields. When a user add content of type 'CT' and Save/Preview the form, I want to use the values that the user added in the form and make a web service call and update the form values based on the data returned from the web service call which would further be saved to database.

I am using hook_node_submit() as below.

function CT_node_submit($node, $form, &$form_state) {
  global $user;
  //dpm($user);
  $nameofuser = $user->name;
  $timezone = $user->timezone;
  $title = $form['field_title']['#value'];
  $pid = $user->uid;
  $pname = $user->name;
  $rurl = $form['field_recording_url']['#value'];
  $purl = $form['field_presenter_url']['#value'];

  $kdetails  = array (
     'nameofuser' => $nameofuser,
'title' => $title,
'pid' => $pid,
'pname' => $pname,
  );
  Make_A_WebService_Call($kdetails, $form, $form_state);
}

The problem is that when I am calling the above code from ABC.module file, the code is not being called on clicking the Save/Preview button.

Answer 1

hook_node_submit() will only be invoked for the module implementing the associated content type. If module A defines the content type, module B cannot implement hook_node_submit() on module A's behalf, unless it specifically calls the function module_B_node_submit().

If you want to hook into the validation process of a node form you can use the standard hook_form_alter(), e.g.

function MYMODULE_form_alter(&$form, &$form_state, $form_id) {
  if ($form_id == 'article_node_form') {
    $form['#validate'][] = 'MYMODULE_node_form_validate';
  }
}

function MYMODULE_node_form_validate($form, &$form_state) {
  // Logic here...
}

Answer 2

In short, you are saying that in the ABC.module you are implemented the CT content type, and you are wondering why ABC_node_submit() (the implementation of hook_node_submit()) is not being invoked.

If ABC_node_submit() is a function contained in ABC.module, then it will be invoked only in the case, the implementation of hook_node_info() is similar to the following one.

function abc_node_info() {
  return array(
    'ct' => array(
      'name' => t('the content type name'),
      'base' => 'ct',
      'description' => t('the content type description'),
    ),
  );
}

(I use lowercase letters since it is preferable that the short name of a module uses only lowercase letters.)

In this case, when invoking hook_node_submit() for that content type, Drupal will look for abc_node_submit().

In fact, in the documentation for hook_node_info(), base is described as follows:

The base string used to construct callbacks corresponding to this node type (for example, if base is defined as example_foo, then example_foo_insert() will be called when inserting a node of that type). This string is usually the name of the module, but not always.

This answer is valid if ABC_node_submit() is a function contained in the ABC.module. If you have two modules (ABC.module and CT.module) where ABC.module is implementing the content type, and CT.module is another module that needs to add a form validation or a form submission handler to the form used to edit a node of that content type, then see Clive's answer.