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To: jwatzman@fb.com
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Message-ID: <20141212154233.145FA261D8D@dd15934.kasserver.com>
Date: Fri, 12 Dec 2014 16:42:33 +0100 (CET)
Subject: Re: [PHP-DEV] [RFC] Nullsafe calls
From: mails@thomasbley.de ("Thomas Bley")

Hello Josh,

1) I think it would be better to have ObjectSafe Calls, e.g.

class User {
  ...
  public function delete() {
    // delete ...
  }
}
class Users {
  public function find($id) {
    if ($this->db->query(...)) return new User($id);
    return 'not found';
  }
}

$users = new Users();
$result = $users->find(42)?->delete(); // $result = 'not found';

That way we can use scalars as return for further processing.

Definition:
Calling $obj?->foo(..) behaves identically to $obj->foo(..) if $obj is an object. If $obj is not an $object, then it returns $obj.


2) Another approach would to implement this in user land:

class Failure {
  public function __construct($msg) {
    $this->msg = $msg;
  }
  public function __call($name, $args) {
    return $this;
  }
}
class User {
  ...
  public function delete() {
    // delete ...
  }
}
class Users {
  public function find($id) {
    if ($this->db->query(...)) return new User($id);
    return new Failure('not found');
  }
}

$users = new Users();
$result = $users->find(42)->delete();
// do sth...
if ($result instanceof Failure) {
  echo $result->msg; // not found
}

Regards
Thomas


Josh Watzman wrote on 10.12.2014 00:07:

> Hey internals! A useful feature that Hack picked up in the last few months are
> "nullsafe calls", a way of propagating failure forward in a series of chained
> method calls to the end of the whole computation, getting rid of a lot of the
> boilerplate in the middle. I think the feature would be a good one for PHP as
> well, so I'm submitting this RFC to add it -- you can see the RFC itself for a
> full discussion of the motivation for the feature, as well as the feature
> itself:
> 
> https://wiki.php.net/rfc/nullsafe_calls
> 
> Josh Watzman
> 
> 
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