Correctly deleting fields from unknown templates

[GuruMeditation]

Hi all, I'm a bit confused with the following issue.

Let's say my module installs a couple of fields (see below) for future use, i.e they are not attached to any templates on install, but the user can add the fields to any templates they want after install.

if(!$this->fields->get('test')) {
  $field_test = new Field();
  $field_test->type = $this->modules->get("FieldtypeText");
  $field_test->name = 'test';
  $field_test->label = 'Test field';
  $field_test->save();
}

if(!$this->fields->get('test2')) {
  $field_test2 = new Field();
  $field_test2->type = $this->modules->get("FieldtypeText");
  $field_test2->name = 'test2';
  $field_test2->label = 'Test field 2';
  $field_test2->save();
}

How exactly do I use the uninstall method to correctly remove them without errors if they have been attached to various templates? I didn't create a fieldgroup for them as they can be independently installed to different templates, so a fieldgroup didn't make sense to me as they are independent fields and not part of a group. But if I use the following code for the uninstall method and they are connected to a template, I get an error and the module can no longer be uninstalled (I have to manually delete the leftovers from the database).

// Array of fields to delete
$fs = array(
  'test',
  'test2',
);
// Delete the fields
$fields = wire('fields');
foreach ($fs as $f) {
  $fields->delete($fields->get($f));
}

Any tips or advice? Cheers

[LostKobrakai]

http://cheatsheet.processwire.com/fields/field-methods/field-getfieldgroups/

This will give you all fieldgroups (aka templates) you need to remove the field from before deleting it.

[GuruMeditation]

Thanks, that makes sense. What would happen if my module deleted the fieldgroup, but other unknown fields were also linked to that fieldgroup? Is it best to actually add my fields to a unique fieldgroup to avoid any conflict with other fields etc?

[LostKobrakai]

I think you're missunderstanding fieldgroups. Fieldgroups hold the fields for templates. Each template does have it's own fieldgroup. You just need to remove your field from the fieldgroup. Do not delete the whole fieldgroup or the template of it won't have fields anymore.

[GuruMeditation]

Ok, I think I get it now. I knocked up the following code which I'll post here in case anyone else finds it useful. It seems to work ok

public function ___uninstall() {

    $fields = wire('fields');

    // Array of fields to delete
    $fs = array(
      'test',
      'test2',
    );

    foreach ($fs as $f) {
      // Get each field from the array above
      $f = $fields->get($f);
      // Get the fieldgroups for each field
      $fgs = $f->getFieldgroups();
      // Loop through each fieldgroup
      foreach ($fgs as $fg) {
        // Remove the field from each fieldgroup it's linked to
        $fg->remove($f);
        $fg->save();
      }
      // Now delete the field
      $fields->delete($f);
    }
}