How should i handle errors in my Codeigniter Models? - php

Question

i am starting to put validation/sanitization in my codeigniter models, and before diving in too deep I am looking for some suggestions on best practices. the form validation library for controllers is great, but obviously i don't want to rely on the controllers to send me good data.
currently I return bool values, TRUE (or data) on success, FALSE on failure, which makes it really hard to pass error messages back to the caller. I would like to get away from the FALSE on failure.
while definitely not an expert, i have started reading quite a bit on Exceptions and have come across them quite a bit with external libraries, and they seem like a good candidate for this. my question is, is this appropriate use of exceptions? are model errors exceptional errors?
a possible example:
<?php
class person_model extends CI_Model{
public function getPersonById($personId){
//check for int
if(!is_int($personId) OR $personId < 0){
throw new Exception('Invalid person ID');
}
//setup query
$this->db->select('*')
->where('personId', $personId);
//run query
$result = $this->db->get('person');
//failed to get
if(!$result){
throw new Exception('DB query failed');
//should i also return false?
return FALSE;
}
//got info
else{
return $result;
}
}
}
?>
thanks for the help!
EDIT:
I have to say I am quite surprised by the responses suggesting that data validation should only be done in the controller. Models are the last barrier to your data storage. The model is the data and the rules applying to that data, your application logic. Data validation seems like application logic to me. Also you may have many controllers accessing the same model method. Do you want to rely on both controllers implementing the same validation? That seems silly to me.
Also, not all data is coming from user input, some of it could be hardcoded into the script by your programmer writing the controller. What if they pass a string when your model is expecting an integer? Or pass an incorrectly formatted date? shouldn't the model say something about that.
I'm open to a discussion, but I feel data validation DEFINITELY belongs in the model. (in addition to the controller, and even the view (html5/javascript for convenience))

Answer 1

the easiest way i've found to deal with this is to always check for the negative condition first with an if check. this also makes it easy to check multiple steps.
always return something back from your model methods whenever possible. Like even in this example - we need to validate the form - i would use codeigniters form validation to validate that its an integer etc. if it passes validation then we need the $personId for the database search. So instead of just returning true/false from the validation - if validation passes then return the $personId :
function getperson() {
// Validate the form
// AND if its valid, return the validated $personId
// Note the separate private method if the validation failed
if ( ! $personId = $this->person->_validateGetPersonForm() ) {
$this->error_msg = 'Error in validating the form. Please use a number.';
$this->_showGetPersonFailed() ; }
elseif ( ! $person = $this->person->getBy($personId) ) {
$this->error_msg = 'There is no person in our records with the number:'. $personId;
$this->_showGetPersonFailed() ; }
else { $this->_showResultsFor($person) ; }
}
$this->error_msg is automatically available for any of your views and because we have broken out validation and the database search - the error message is easily appropriate for the exact condition. if the search failed then there is a private method _showGetPersonFailed() to show the form again. the last if / else is usually success - there is a separate private method to handle showing the results with the appropriate views.
also suggest not using the word "model" in the file name like "person_model". it just clutters up the overall naming and forces you to type the word model over and over again :-) think of it this way: if you are calling something from a controller and getting back results - its almost always going to be a model. and all your model files will always be in a folder named models.

Answer 2

Go to:
application/config/database.php
and search for db_debug to be TRUE. For example:
...
$db['default']['dbprefix'] = '';
$db['default']['pconnect'] = TRUE;
$db['default']['db_debug'] = TRUE; //<-- Have this to true
$db['default']['cache_on'] = FALSE;
$db['default']['cachedir'] = '';
...

Answer 3

In my models, I never throw exceptions or errors. I always return false on a query that returns null. If there is an SQL error in your code you will be notified by codeigniter automatically. I would stay away from throwing exceptions if your query returns no results.
You can then handle the query if it returns false with your controller.
EDIT: Also you should check the data being queried into the database in the controller, and not the model. In my opinion the model should be used strictly for querying data, not for error/data checking, you can do this before hand in the controller when it is submitted.
An example:
Model
function search_replies($term){
$this->db->like('ticket_id', $term);
$this->db->or_like('reply_from', $term);
$this->db->or_like('reply_from_name', $term);
$this->db->or_like('reply_content', $term);
$query = $this->db->get($this->table_ticket_replies);
// Returns the result if the number of rows is greater than 0, returns false otherwise
if ($query->num_rows() > 0) return $query->result();
return false;
}
Controller
function example_controller(){
if($this->search_model->search_replies('Test')){
$data['results'] = $this->search_model->search_replies('Test');
}
$this->load->view('search_results', $data);
}
View
<?php
if(isset($results)){
echo 'Retrieved Results';
foreach($results as $result){
}
} else{
?>
<h2>No results for search term!</h2>
<?php
}
?>

Answer 4

You have probably missed out this part of the form validation page in the user guide:
Showing Errors Individually
Usage:
echo form_error('field_name');
Just put in whatever field name you are using in place of "field_name", for example "username" or "email" etc.