Comments on: Caching dependency-injected objects

By: Dave

Dave — Fri, 26 Mar 2010 08:32:32 +0000

Interesting idea regarding the use of the Observer pattern, Mark. I must admit I haven’t yet got into any optimisations. I will have to get a profiler on it at some point.

By: Dave

Dave — Fri, 26 Mar 2010 08:25:58 +0000

Some interesting points Giorgio. I accept that I shouldn’t use __!

Using setter rather than construction injection may be a good way to go regarding reusing the interface. My __restoreDependencies method could be simply setDependencies to make things simpler.

However the problem would still remain that the injection would not be performed automatically after unserialize().

By: Mark Baker

Mark Baker — Thu, 25 Mar 2010 20:41:55 +0000

An excellent article
I’ve been working on something similar myself, using the observer pattern with my cacheable objects to trigger the caching whenever they are modified in any way. Surprisingly, I found that it was more efficient in terms of execution time to call a detach() method to set the observer property to null rather than use the __sleep() magic method. Perhaps it was the overhead of needing to return an array of the properties that I did want serializing, and it might vary from object to object.
While I haven’t had any problems with caching to APC, memcache, a disk file, or php://temp; I’ve found that caching the serialized objects to a simple array is giving me intermittent memory leakage. Despite setting the observer property of the objects to null before serializing, I’m still getting orphaned instances left in the memory, as I would if the the observer property refcount wasn’t yet 0. I’m wondering if the garbage clearance hasn’t kicking in quickly enough to clear the cyclic reference.

By: Jonathan Nieto

Jonathan Nieto — Thu, 25 Mar 2010 19:44:46 +0000

Really interesting!

Thanks for sharing!

By: Giorgio Sironi

Giorgio Sironi — Thu, 25 Mar 2010 18:25:36 +0000

Maybe using setter injection instead of constructor injection you can reuse the same interface for a) injection of collaborators and b) waking up. I mean substituting the __construct() parameters with a few initXXX() methods which accept an object if the correspondent field property is not already set. After de-serialization the properties are null so the init*() methods work again.
Anyway, you shouldn’t use methods that start with __. They are reserved for future use and convey a bad semantic (no magic behavior).