How to AJAX refresh field on change of another in editor?

[hellomoto 40]

I have a manufacturers page select field and a dependent models one with pages of template `model` which are allowed children of pages with template `manufacturer`. So I have this as the findPagesCode for the models page options field:

return $page->manufacturer->children();

However this requires the page be saved in order to display options. This is not ideal. 

I have a singular autoload module with the following:

public function init() {
    $this->pages->addHookAfter('render', $this, 'filterModels');
}
public function filterModels($event) {
    $page = $event->arguments('page');
    if($page->template != 'boat_vessel') return;
    $this->message("models filter");
}

It's doing nothing. 

I was thinking I could work out something with this example but I would need the above test to be working first anyway...

$this->pages->addHookAfter('changed', function(HookEvent $event) {
  $page = $event->object;
  $change = $event->arguments(0);
  if($page->template == 'boat_vessel' && $change == 'manufacturer') {
    // execute some code 
  }
});

But what? How do I refresh the models field?

Is there a way to do this in the field settings? I would think in the custom PHP textarea that `return $page->manufacturer->children();` would work but it doesn't. 

[hellomoto 40]

Actually it does, but you have to save the page to get the childpages field options.

How can I auto-save the parentpage field on selection change and immediately subsequently auto-refresh the childpage field?

[hellomoto 40]

I'm trying to alter some code I used to do something similar (fields for selected template) on another project (here) and so far just this simple direct snippet is not doing anything:

  public function init() {
    $this->pages->addHookAfter('render', $this, 'filterModels');
  }

  public function filterModels($event) {
    $page = $event->arguments('page');
    if($page->template != 'boat_vessel') return;
    $this->message("models filter");
  }

The module is active... Why no results?

[Robin S 4,497]

There is limited (and undocumented) AJAX 'dependent selects' support built into Page Reference fields. You must use the 'Custom find' or 'Selector string' option for defining selectable pages, and reference the source Page Reference field (that exists on the same page) using syntax like this:

parent=page.page_reference_field_name

Based on testing I have found:

• It only works for Select, Select Multiple or AsmSelect inputfields
• It does not work inside a repeater item

Edited June 5, 2017 by Robin S
Included 'Custom find'

[hellomoto 40]

Thank you.