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: marrtins at dqdp dot net
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:
I completely agree such is_initialized() would be useful for typed properties. Another use case
would be for passing data to database.
Distinction would be useful:
If property hasn't been initialized - ignore it.
If property has been set to null - set database field to null.
Previous Comments:
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[2020-12-04 10:50:17] a dot haan at iwink dot nl
Ah. With https://bugs.php.net/bug.php?id=78904
that behavior of __get changed. There's now a difference between uninitialized and
unset properties.
That makes this request more apparent.
We used to mix types for micro cache properties; start as false, ending up with
null, or an object instance. By strict checking for false retrieval is
only done once.
Since mixing types is a bad practice, and not an option with typed properties anyway, it would be
ideal if one could detect whether a property was actually uninitialized.
Sure, we can. Two ways are mentioned here. But both are verbose and require representing the
property as a string.
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[2020-12-04 10:15:52] a dot haan at iwink dot nl
[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.
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[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.
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[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.
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[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.
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