PHP exception and user message - php

Question

I have a project object.
A user can assign a worker object for it.
99% of the case the project object has all the proper fields set.
In some cases, the project is missing a field.
In order for a worker to be assign to a project the project must have all the required fields setup.
To solve this, I throw exceptions like this: ( don't try to find a pattern here, the real example is more complex )
if ($project->startDate == false ) {
throw new Exception("Missing startDate attribute for project id: $id");
}
if ($project->finishDate == false ) {
throw new Exception("Missing finishDate attribute for project id: $id");
}
if ($project->startDate > $project->finishDate ) {
throw new Exception("Invalid start date for project id: $id");
}
The problem with this is that I need to display a custom message to the user each time. For example if the first error is thrown the user should see: 'Please setup the project start date' and so on.
How can I do this ?

Answer 1

Just define your own exception class and your whole code in a try .. catch:
class FormException extends Exception {
private var $userMessage;
public function __construct($message, $userMessage) {
parent::__construct($message);
$this->userMessage = $userMessage;
}
public function getUserMessage() {return $this->userMessage;}
}
try {
// Whole code goes here, probably a function call
throw new FormException("Missing startDate attribute for project id: $id",
'Please setup the project start date');
} catch (FormException $e) {
echo $e->getUserMessage();
error_log($e->getMessage());
}
By the way, if you want to include variable contents in a string, either use double quotes ("id: $id") or concatenate ('id: ' . $id).

Answer 2

Try this:
try
{
$Message = '';
if ($project->startDate == false ) {
$Message = "Please setup the project start date\n";
throw new Exception("Missing startDate attribute for project id: $id");
}
if ($project->finishDate == false ) {
$Message = "Please setup the project finish date\n";
throw new Exception("Missing finishDate attribute for project id: $id");
}
if ($project->approved == false ) {
$Message = "Please setup the project approved field\n";
throw new Exception("Missing approved attribute for project id: $id");
}
}
catch(Exception $Ex)
{
// Log in some way you like the $Ex-getMessage();
echo nl2br($Message);
}

Answer 3

Inside your project class, create a new method, probably called getErrorMessage.
That function should do the checks (no need to have the concrete way of validation outside of project or create a validation object for project). Then:
if ($message = $project->getErrorMessage())
{
throw new Exception(sprintf('%s (project id: %d)', $message, $id));
}
If you decide to not throw exceptions for design reasons, this still is of use.
You gain more flexibility with a validator object that can naturally provide more detailed information than a single method. So it might be the better thing to do:
class ProjectValidator
{
private $project;
private $errors;
public function __construct($project)
{
$this->project = $project;
}
public function isValid()
{
// run your checks, add errors to the array as appropriate.
$errors = array();
if (!$this->project->startDate)
{
$errors[] = 'Missing startDate attribute';
}
if (!$this->project->finishDate)
{
$errors[] = 'Missing finishDate attribute';
}
if (!$this->project->approved)
{
$errors[] = 'Missing approved attribute';
}
$this->errors = $errors;
return (bool) count($this->errors);
}
public function getErrors()
{
return $this->errors;
}
}
$validator = new ProjectValidator($project);
if (!$validator->isValid())
{
// throw an exception or do whatever you want in case it's not valid
$errors = $validator->getMessages();
$message = sprintf("Project id: %d has the following %d error(s):\n", $id, count($errors));
foreach($errors as $index => $error)
{
$message .= sprintf("%d. %s\n", $index+1, $error);
}
throw new Exception($message);
}