Question

Can I please have a design suggestion for the following problem:

I am using Codeigniter/Grocery_CRUD.

My system is multi tenanted – different autonomous sites – within the same client. I have quite a few instances of tables that have unique logical keys. One such table structure is:

equip_items
id (pk)
equip_type_id (fk to equip_types)
site_id (fk to sites)
name

Where (equip_type_id, site_id, name) together are a unique key in my db.

The issues is that when using a grocery_CRUD form to add or edit a record that breaks this database rule – the add or edit fails (due to the constraints in the db) but I get no feedback.

I need a variation on the is_unique form_validation rule by which I can specify the field*s* that must be unique.

The issues:
How to specify the rule? set_rules() is for a given field and I have multiple fields that the rule will apply to. Does that mean I should abandon the Form_validation pattern? Or do I follow the ‘matches’ rule pattern and somehow point to the other fields?

Perhaps a callback function would be better but this would mean writing a custom function in each model where I have this problem at last count this is 9 tables. It seems far better to do this in one place (extending form_validation).

Am I missing something already in codeigniter or grocery_CRUD that has already solved this problem?

Any suggestion/advice you might have would be appreciated.

EDIT:
Actually it appears the solution Johnny provided does not quite hit the mark – it enforces each field in unique_fields() being independently unique – the same as setting is_unique() on each one. My problem is that in my scenario those fields are a composite unique key (but not the primary key). I don’t know if it is significant but further to the original problem statement: 1) site_id is a ‘hidden’ field_type – I don’t want my users concerned they are on a different site so I’m dealing with site_id behind the scenes. 2) Same deal with an equip_status_id attribute (not part of the unique key). And 3) I have set_relations() on all these foreign key attributes and grocery_CRUD kindly deals with nice drop downs for me.

EDIT 2
I have solved this using a callback.

Answer 1

UPDATE: This code is now part of grocery CRUD version >= 1.4 and you don’t need to use an extension anymore. For more see the documentation for unique_fields

I will try to explain it as easy as I can:

1. First of all for those who have grocery CRUD lower or equal to 1.3.3 has to use this small change: https://github.com/scoumbourdis/grocery-crud/commit/96ddc991a6ae500ba62303a321be42d75fb82cb2

2. Second create a file named grocery_crud_extended.php at application/libraries

3. Copy the below code at your file application/libraries/grocery_crud_extended.php

<?php 
class grocery_CRUD_extended extends grocery_CRUD
{
    protected $_unique_fields = array();

    public function unique_fields()
    {
        $args = func_get_args();

        if(isset($args[0]) && is_array($args[0]))
        {
            $args = $args[0];
        }

        $this->_unique_fields = $args;

        return $this;
    }

    protected function db_insert_validation()
    {
        $validation_result = (object)array('success'=>false);

        $field_types = $this->get_field_types();
        $unique_fields = $this->_unique_fields;
        $add_fields = $this->get_add_fields();

        if(!empty($unique_fields))
        {
            $form_validation = $this->form_validation();

            foreach($add_fields as $add_field)
            {
                $field_name = $add_field->field_name;
                if(in_array( $field_name, $unique_fields) )
                {
                    $form_validation->set_rules( $field_name, 
                            $field_types[$field_name]->display_as, 
                            'is_unique['.$this->basic_db_table.'.'.$field_name.']');
                }
            }

            if(!$form_validation->run())
            {
                $validation_result->error_message = $form_validation->error_string();
                $validation_result->error_fields = $form_validation->_error_array;

                return $validation_result;
            }
        }
        return parent::db_insert_validation();
    }

    protected function db_update_validation()
    {
        $validation_result = (object)array('success'=>false);

        $field_types = $this->get_field_types();
        $unique_fields = $this->_unique_fields;
        $add_fields = $this->get_add_fields();

        if(!empty($unique_fields))
        {
            $form_validation = $this->form_validation();

            $form_validation_check = false;

            foreach($add_fields as $add_field)
            {
                $field_name = $add_field->field_name;
                if(in_array( $field_name, $unique_fields) )
                {
                    $state_info = $this->getStateInfo();
                    $primary_key = $this->get_primary_key();
                    $field_name_value = $_POST[$field_name];

                    $ci = &get_instance();
                    $previous_field_name_value = 
                        $ci->db->where($primary_key,$state_info->primary_key)
                            ->get($this->basic_db_table)->row()->$field_name;

                    if(!empty($previous_field_name_value) && $previous_field_name_value != $field_name_value) {
                        $form_validation->set_rules( $field_name, 
                                $field_types[$field_name]->display_as, 
                                'is_unique['.$this->basic_db_table.'.'.$field_name.']');

                        $form_validation_check = true;
                    }
                }
            }

            if($form_validation_check && !$form_validation->run())
            {
                $validation_result->error_message = $form_validation->error_string();
                $validation_result->error_fields = $form_validation->_error_array;

                return $validation_result;
            }
        }
        return parent::db_update_validation();
    }   

}

4. Now you will simply have to load the grocery_CRUD_extended like that:

    $this->load->library('grocery_CRUD');
    $this->load->library('grocery_CRUD_extended');

and then use the:

$crud = new grocery_CRUD_extended();

instead of:

$crud = new grocery_CRUD();

5. Now you can simply have the unique_fields that it works like this:

$crud->unique_fields('field_name1','field_name2','field_name3');

In your case:

$crud->unique_fields('equip_type_id','site_id');

Pretty easy right?

This is checking if the field is unique or not without actually change the core of grocery CRUD. You can simply use the grocery_CRUD_extended instead of grocery_CRUD and update grocery CRUD library as normal. As I am the author of the library I will try to include this to grocery CRUD version 1.4, so you will not have to use the grocery_CRUD_extended in the future.