Re: Proposal: new magic methods for Object references.

2013/3/19 Matīss Roberts Treinis <mrtreinis@gmail.com>: > Proposal: > > Two additional magic methods for PHP objects - > > __refer(void): > > Refer method is called whenever object's identifier is assigned to > variable, if such method is present. > Example: > > $foo = new Bar; > $bar = $foo; //__refer invoked > > Return values: null to proceed by assigning the variable to objects > identifier. Any other value returned would be assigned to variable > which is to hold the reference in case of null. > > __unrefer($var): > > Unrefer method would be called whenever object's identifier is about > to be replaced by anything else and would hold that something else as > argument. > Example: > > $foo = new Bar; > $foo = false; //__unrefer invoked with false as argument > > Return values: null to proceed with default by replacing value, false > to not to replace value and keep the reference in variable. > > Real life use sample: > > class SomeObject{ > protected $count; > function __refer(){ > $this->count++; > } > } > > $foo = new Bar; > $bar = $foo; > $foobar = $bar; //SomeObject::$count = 2 > > ---------------------------------------------------- > > class SomeCustomString{ > protected $value; > function __unrefer($value){ > if(is_string($value)){ > $this->value = $value; > } > throw new UnexpectedValueException('This object can only hold strings'); > } > } > > $foo = new SomeCustomString; > $foo = 1; > > ------------------------------------------------------ > > Although I can't think of many uses to __refer I however can think of > one very useful use case for __unrefer - custom "types". I actually > did borrow the __unrefer functionality from SPL_Types PECL package > when trying to solve problem of how to validate contents of object > properties which are going to be set by other party and cant be > validated via set or get. I know there are ways to do this, but none > seemed pretty enough for me to actually implement. > > Any feedback on this is very welcome, especially from core developers > and potential users. What would be the issues, potential drawbacks, > other? For sure: *lot* of overhead on any object assignments: checking whether __refer() exist on the variable being assigned and whether __unrefer() exist on the destination variable. > Separate question to core developers would be, how hard it would be to > implement such functionality, or is this even possible with reasonable > effort? > > Thanks, regards > Matiss Roberts Treinis <mrtreinis at gmail dot com>