C#'s "using" statement

at 2006-10-22 in Further reading by friebe (0 comments)

Having blogged about Python's new with statement (see entry #117), I decided I'll also mention C#'s using() which is quite similar.

From the C# Reference:

Defines a scope, outside of which an object or objects will be disposed.

Example:

  using (TextWriter w= File.CreateText("log.txt")) {
    w.WriteLine("This is line one");
  }

The above code is a shorthand for:

  TextWriter w = File.CreateText("log.txt");
  try {
    w.WriteLine("This is line one");
  } finally {
    if (w != null) { ((IDisposable)w).Dispose(); }
  }

...and is actually translated by the C# compiler to the latter (see also Understanding the 'using' statement in C#).

Possibilites
Now think about the possibilities this gives us when creating our own implementations of the Dispose() method. Here's one:

  using (Transaction t= connection.BeginTransaction()) {
    // ... performs inserts, updates, deletes...
    t.commit();
  }

(see also Easier Database Transactions - Extending the Using Statement...).

Would this make sense in PHP?
For core PHP, using() would only have limited use, as most functions such as fopen() or mysql_connect() won't actually throw exceptions but rather return FALSE (or NULL, or -1, it's not that they're really consistent with this

).

For the new object-oriented extensions such as PDO, or of course within the XP framework, this would be a great addition though.

Idea:

<?php 
  $conn= DriverManger::getConnection($dsn);
  using ($conn->begin(new Transaction('update_person')) as $t) {
    $conn->query('update person ...');
    $conn->query('insert into synchronization ...');
    $t->commit();
  }
?>

If you're wondering why there's no RFC on this: Implementing this in PHP userland is not possible without having to pass the entire sourcecode within the using block as a string, which seems quite ugly (see this experiment).

If there were to be using() for PHP, it should really go into the PHP core. Or, of course, into a preprocessor / translator of some sort - but that's a different story

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C#'s "using" statement

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