Many times i find this redundan开发者_运维知识库t:
$found = $repo->findOneByCode($code);
$zone = isset($found) ? $found : new Zone();
Can anyone suggest a better way, similar to (not working):
$zone = $repo->findOneByCode($code) || new Zone();
EDIT: i can't modify Zone
and findOneByCode
as they are auto-generated classes and function by Doctrine ORM.
If you're using >= PHP 5.3
$zone = $repo->findOneByCode($code) ?: new Zone();
otherwise maybe this is better? (still a bit ugly)...
if ( ! ($zone = $repo->findOneByCode($code))) {
$zone = new Zone();
}
Assuming on failure, $repo->findOneByCode()
returns a falsy value...
What you're describing is a lazy singleton pattern. This is when there is only ever one instance of the class, but it doesn't get initialized until you try to use it.
Example: http://blog.millermedeiros.com/2010/02/php-5-3-lazy-singleton-class/
You can do the following:
$zone = ($z = $repo->findOneByCode($code)) ? $z : new Zone();
Note, however, that this does not work exactly like using isset()
. While using isset()
will allow other falsey values other than NULL
to pass through (such as FALSE
), using a ? b : c
will resolve to c
on all falsey values.
These two methods will also do the job:
$zone = $repo->findOneByCode($code) or $zone = new Zone();
($zone = $repo->findOneByCode($code)) || ($zone = new Zone());
Note that or
and &&
have different precedences and that is why we need the () in the second example. See http://www.php.net/manual/en/language.operators.logical.php. The example there is:
// The result of the expression (false || true) is assigned to $e
// Acts like: ($e = (false || true))
$e = false || true;
// The constant false is assigned to $f and then true is ignored
// Acts like: (($f = false) or true)
$f = false or true;
var_dump($e, $f);
And the result:
bool(true)
bool(false)
This is because and
and or
have lower precedence than =
meaning the assignment will be done first. On the other side, &&
and ||
have higher precedence than =
meaning the logical operation will be done first, and its result assigned to the variable. That is why we cannot write:
$result = mysql_query(...) || die(...);
$result
will hold the result of the logical operation (true or false). But when we write:
$result = mysql_query(...) or die(...);
the assignment is done before the logical operation. And if it is not falsely value, the part after the or
is cimpletely ignored.
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