Req #78480 [Com]: The typed properties miss an important "function"
Edit report at https://bugs.php.net/bug.php?id=78480&edit=1
ID: 78480
Comment by: a dot haan at iwink dot nl
Reported by: manchokapitancho at gmail dot com
Summary: The typed properties miss an important "function"
Status: Open
Type: Feature/Change Request
Package: Scripting Engine problem
PHP Version: 7.4.0beta4
Block user comment: N
Private report: N
New Comment:
[2019-09-08 18:10 UTC] jhdxr@php.net writes:
You can use __get to check if it's initialized.
That's not completely true - in PHP 7.4.11.
In the first example on https://wiki.php.net/rfc/typed_properties_v2#overloaded_properties
if you do not include unset($this->typed);, then that example still throws:
Fatal error: Uncaught Error: Typed property Test::$typed must not be accessed before initialization
in test.php on line 24
That line is the first var_dump($test->typed);.
Apparently this little edge case was not covered when implementing the RFC.
Regarding this mentioned issue there is another option to test for initialized state:
array_key_exists('prop', get_object_vars($obj));
Not very neat either.
Previous Comments:
------------------------------------------------------------------------
[2019-09-09 18:10:12] manchokapitancho at gmail dot com
I know that I can use __get but:
1. this is a workaround (which is also not simpler than a ReflectionProperty call).
2. this is only possible if the developer has control over the class. A counterexample would be a
typed property in a class exposed by a third party library.
Once again: the target is "if (!is_initialized($obj->prop)) { ... }" similar to
"if (!isset($obj->prop)) { ... }". Isset would not generate a notice if the property is
not defined and similarly is_initialized should not trigger a TypeError if $obj->prop has not
been yet initialized.
------------------------------------------------------------------------
[2019-09-08 18:10:54] jhdxr@php.net
You can use __get to check if it's initialized.
see the Overloaded Properties section of the RFC(https://wiki.php.net/rfc/typed_properties_v2) as an
example.
------------------------------------------------------------------------
[2019-08-31 14:05:20] manchokapitancho at gmail dot com
A simplified use case would be:
//orm with lazy loading from DB
class something {
public ?<class|self> $parent;
....
function getParent() {
if (! is_initialized($this->parent)) {
$this->parent = //fetch from DB; value could be NULL
}
return $this->parent;
}
...
}
A plain function is indeed possible but the call parameters should be ($obj, 'prop) since
($obj->prop) would throw TypeError.
------------------------------------------------------------------------
[2019-08-31 11:42:08] nikic@php.net
What's your use-case?
A language construct for this is very unlikely, but if this is a common and performance-critical
operation, a plain function could be provided in lieu of going through reflection.
------------------------------------------------------------------------
[2019-08-30 21:27:50] manchokapitancho at gmail dot com
Description:
------------
The new PHP 7.4 feature - typed properties is a great addition to the language.
As a side effect it adds a brand new state of the class/object properties - initialized=yes/no.
If one tries to access an uninitialized property, a TypeError is being thrown.
isset($object->prop) does not trigger TypeError but it returns false if $object->prop is NULL.
The suggested check is only indirectly possible via the long construct
(new ReflectionProperty(<name>::class, '<prop>'))->isInitialized($obj)
On the other side, unset works perfectly well and returns a property back into the uninitialized
state.
This write-only asymmetry is not consistent and I would expect a language construct similar to isset
[e.g. is_initialized($obj->prop)] that handles this case.
Test script:
---------------
class test {
public ?int $prop;
}
$obj = new test;
var_dump(isset($obj->prop));
var_dump(is_initialized($obj->prop));
$obj->prop = null;
var_dump(isset($obj->prop));
var_dump(is_initialized($obj->prop));
Expected result:
----------------
false
false
false
true
Actual result:
--------------
false
<missing>
false
<missing>
------------------------------------------------------------------------
--
Edit this bug report at https://bugs.php.net/bug.php?id=78480&edit=1
Thread (10 messages)