revert_data()

[david63]

I know with an extension that when the "Delete data" is run the extension will try to remove the update_data() that is in the migration file and that there is the option to control what is removed by using the revert_data() function.

So I have a two part question:

1. If there is a revert_data() function present will it only delete the data in that function or will it carry out the delete from the update_data() function but overwrite that by what is in the revert_data() function - in other words if I have a revert_data() function do I have to put everything in there?

2. How do I test to ensure that a module is empty before I try to remove it. For example if I create a module, say, array('module.add', array('acp', 'ACP_CAT_USERGROUP', 'ACP_MY_MODULE')) into which I then add further modules from more than one extension (the "top level" would be created in each extension if necessary) when the delete data comes along for one of the extensions it will give an error if there is still another item in the "top level" module.

[MattF]

1. An update_data() method will always be reverted (or attempted). The revert_data method is only for things the migrator can't automatically revert, such as custom methods. So no, you don't have to put everything in it, just new custom methods to revert your update_data()'s custom methods.

2. Write a query to check if your "parent" module has any "children". The way to know if it has children is if right_id - left_id > 1 is true. Empty would mean that code evaluates to false.

[MattF]

For example:

Code: Select all

'SELECT module_id
FROM ' . $this->table_prefix . "modules
    WHERE module_class = 'acp'
        AND module_langname = 'ACP_MY_MODULE'
        AND right_id - left_id > 1";
$result = $this->db->sql_query($sql);
$module_id = (int) $this->db->sql_fetchfield('module_id');
$this->db->sql_freeresult($result);

// return true if module is empty, false if has children
return (bool) !$module_id;

[david63]

Thanks - I was hoping that it would have been something a bit easier such as "if not empty" or some such.