> Am 25.11.2014 um 22:26 schrieb Marc Bennewitz:
>
>> Hi internals,
>>
>> In OOP it's a sometimes a common issue to know the state of an object and
>> to know if it was changed respectively it it can change state.
>>
>> We already have such objects like DateTImeImmutable and new proposed
>> objects like UString also introduce immutable objects.
>>
>> I think it would be really helpful to see this kind of issue addressed in
>> a standardized way:
>>
>> if you approve with this I would write down a more structured RFC.
>>
>> Now see the following code snipped:
>>
>> <?php
>>
>> immutable class MyImmutableClass {
>> public static $staticProperty = 'private static';
>> public $ts;
>> public $obj;
>>
>> public function __construct($obj = null) {
>> $this->ts = time();
>> $this->setObj($obj);
>> }
>>
>> public function getTimestamp() { return $this->ts; }
>> public function getObj() { return $this->obj; }
>> public function setObj($obj) { $this->obj = $obj; }
>> }
>>
>> // initialize
>> $obj = new DateTImeImmutable();
>> $obj = new MyImmutableClass($obj);
>>
>> // check if immutable
>> var_dump(MyImmutableClass::immutable);
>> var_dump($obj::immutable);
>>
>> // read properties
>> var_dump($obj->ts, $obj->obj);
>> var_dump($obj->getTimestamp(), $obj->getObj());
>>
>> // ERROR: Immutable objects can not contain mutable properties
>> $obj = new MyImmutableClass(new stdClass);
>>
>> // ERROR: Immutable objects can not be changed after initialization
>> $obj = new MyImmutableClass();
>> $obj->setObj($obj);
>> $obj->obj = $obj;
>>
>> // ERROR: It's not allowed to change immutable variables
>> MyImmutableClass::$staticProperty = 'new value';
>>
>> ?>
>>
>> Because of for immutable objects it's not allowed to set an mutable object
>> as property
>> you can be sure the object's state will be consistent. That's the main
>> difference from
>> marking all properties readonly or similar functionalities.
>>
>> Additionally it's simple to test if an class/object is immutable and
>> document it for free.
>>
>> Downside: New Keyword "immutable"
What I think is more useful is C++'s const, which basically makes any
structure immutable when you need it. However, I don't think it's
worth going through the effort to bring this to PHP, as you would have
to add checks for preventing state changes in many places at runtime.
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