Is it possible to get the Model error code inside the controller in CakePHP?

Question

I have a simple unsubscribe function in my Unsubscribed controller.

if ($this->Unsubscribe->save($this->data['Unsubscribes'])) {
   // success
   $this->Session->setFlash('Your email has been unsubscribed!');
   $this->redirect('/unsubscribes/unsubscribe');
} else {
   // error
   $this->Session->setFlash('There was an error!');
   $this->redirect('/unsubscribes/unsubscribe');
}

Here is the problem. I want to set the email address in the database as unique. So if someone enters the email address multiple times (or we already have it in our unsubscribe list), we are not populating the database with duplicate records. However, I want the visitor to know they have been added to the database (so they know they are unsubscribed).

Is there a way to detect the Duplicate entry error from the controller so I can equate that to a success? The caveat, I don't want to create a extended app_model. Any ideas? Can it be done? How is the best way to do this?

SOLUTION: Here is the final solution I implemented. I added the validation (as suggested by the chosen answer below) and I updated my controller as follows:

// error
if(isset($this->Unsubscribe->validationErrors['email'])){
   $error = 'Your email has been unsubscribed!';
} else {
   $error = 'Something went wrong. Please try again.';
}

$this->Session->setFlash($error);
$this->redirect('/unsubscribes/unsubscribe');

Answer 1

I think you can do it like this:

if ($this->Unsubscribe->find('count',array('conditions'=>array('email'=>$this->data['Unsubscribes']['email']))) > 0   )
{
   $this->Session->setFlash('duplicate email!');
   $this->redirect('/unsubscribes/unsubscribe');
}
//then do your stuff 

Answer 2

It depends. Is there any other error that might occur that you want to display? Or is this the only error that may occur? In case of the latter, just don't check:

$this->Unsubscribe->save($this->data['Unsubscribes']);
// I don't care if that actually saved or not,
// unless something horrible happened the email is in the database
$this->Session->setFlash('Your email has been unsubscribed!');
$this->redirect('/unsubscribes/unsubscribe');

Otherwise, you can use the invalidFields() method to find out what went wrong.

Answer 3

What about using the isUnique validation rule? Then just use the validation error to inform the user.

var $validate = array(
    'login' => array(
        'rule' => 'isUnique',
        'message' => 'This username has already been taken.'
    )
);

Stole this directly from the cookbook. Section 4.1.4.14 isUnique to be precise.