Set Mailable header via a trait? - laravel

Question

I'm creating a Laravel package that would benefit from the use of emails. When a user would use my package they would want to email a file created by the package, but also set some custom headers for the email.
In an ideal solution, I would like to have a trait that the developer could simply use on their mailable class and it would automatically set the header for that email without any additional code. Is this something that is even possible via the use of a trait?
Some solutions have suggested adding headers to mailables by putting this in the build method:
$this->withSwiftMessage(function ($message) {
$headers = $message->getHeaders();
$headers->addTextHeader('mime', 'text/calendar');
});
But is there some way to have my own custom trait piggy-back on the build method of the Mailable that is using it WITHOUT having to write it in the Mailable class itself?

Answer 1

SOLUTION USING TRAITS
The only way to be able to do that with a trait would be defining the build method in your trait and make your user define another function instead of build such that you have the direct manipulation of the function actually used by Mailable class.
So your trait would be:
trait IsMailable {
public function build()
{
$this->withSwiftMessage(function ($message) {
$headers = $message->getHeaders();
$headers->addTextHeader('mime', 'text/calendar');
});
if(!method_exists($this, 'buildMail')) throw \Exception('buildMail is not defined!');
return $this->buildMail();
}
}
So your user will have to define the method buildMail instead of build.
OPTIMAL SOLUTION
The optimal solution, IMHO, would be extending the class Illuminate\Mail\Mailable redefining the method send and making the end user implement this newly defined class instead of Illuminate\Mail\Mailable.
So your class would be:
class Mailable extends \Illuminate\Mail\Mailable {
/**
* Send the message using the given mailer.
*
* #param \Illuminate\Contracts\Mail\Mailer $mailer
* #return void
*/
public function send(MailerContract $mailer)
{
$this->withSwiftMessage(function ($message) {
$headers = $message->getHeaders();
$headers->addTextHeader('mime', 'text/calendar');
});
parent::send($mailer);
}
}
Doing that your user can use the build method as it would do using the standard Illuminate\Mail\Mailable class but the end result would be that your class is piggybacking the additional information that you actually need.