PHP composition

[c_pattle]

I'm having a bit of trouble using composition.  I have a function in a class that uses composition.  Here is that function. 

 

function emailDetails() {
	$this->to = "hello@example.com";
	$this->subject = "Login Details";
	$this->message = "Here are your login details";
	return new emailClass($this);
}

 

Then in the "emailClass" the __construct function looks like this. 

 

    function __construct(&$user){
        $this->user=&$user;
$this->to = $this->user->to;
$this->from = "someone@example.com";
$this->subject = $this->user->subject;
$this->message = $this->user->message;
    }

 

This all works fine but my problem is that I then can't use the "emailClass" on it's own because it requires an instance of a class to be passed to it in it's construct.  Is this a poor case of design on my part?

 

 

[KevinM1]

Well, first, if you're using PHP 5 you don't need to pass the User instance by reference.  Objects are automatically passed by reference.

 

But, yeah, your design is messed up.  Your Email class shouldn't require a User to work, right?  Logically, email is a utility service.  It should be able to be used throughout your system.  This is one of the reasons why I suggested turning it into a static class (all methods marked as static) in your previous thread on this subject.

 

If you're determined to use composition, it makes more sense for the User to contain the Email.  Why?  Because it's the User which depends on the Email functionality being present.  Email is a component (hence composition) of the User.

[ignace]

Your design is FUBAR! You are assigning Email properties to your User. In DDD, when you have 2 objects that should work together, but passing either object to the other is awkward, use a Service. I'm not for the make all Email methods static approach as it creates a hard dependency between either User and Email or vice versa.

[KevinM1]

Can you give a code example of a Service?

[ignace]

class PostOfficeService {
    public function send(Email $email, User $to) {
        $email->addTo($to->getEmailAddress());
        $email->send();
    }
}

 

Neither User nor Email now need to know about the other, providing greater flexibility in your design.

[KevinM1]

Ah, nice.

[ignace]

Scratch that. The example is quiet lame, but the intention should be clear. Remove the dependency between either objects (Model:User and Infrastructure:Email).