Wojciech Sznapka Blog – PHP / Symfony 2 / Open Source » Loosening dependencies with closures in PHP

Loosening dependencies with closures in PHP

Today I ran into a little issue: how to pass generic logger object to method? I wanted to get some verbose output from method, which I call from Command, but onc time it should log with Symfony2 OutputInterface and other time it should use monolog logger. Of course I can make some wrapper class for both of them, but it would be kind of an overkill. The Closure from PHP 5.3 came with solution. In calling method I created closure like this:

On the second hand I’ve got:

As you can see I don’t need to care about logging – just call the closure with message and it will log it properly, depending on context.

Radosław Mejer

It’s not safe to use ‘Closure’ as type hint.

PHP Manual states that “Anonymous functions are currently implemented using the Closure class. This is an implementation detail and should not be relied upon. ”

I think it’s better to check if the first argument is callable. Than You can use array callback as well.
http://sznapka.pl wowo

That’s true, good point. Thanks for feedback :-)
http://www.rooftopsolutions.nl/ Evert

You said thank you but didn’t fix it ^_^. In PHP 5.4 there will be a ‘callable’ type hint, which is the only good way to do it.
Koen

Besides, it is not clear from \Closure what the closure does. You rely on it logging what you put in it. You might just as well loosen dependencies by removing any type hinting or use Object if that was available.
http://sznapka.pl wowo

@Koen
not excatly. If I remove type hinting I don’t know which method I should use in my service (once it can be writeLn(), other time warning() or log()). With \Closure I can pass message as a param and it will handle it somehow, depends on context where it came from.
@Radosław Mejer and @Evert
Maybe I shouldn’t depend upon \Closure type, but it works for now (and probably will work few years ahead). Both Symfony and Doctrine2 uses \Closure as type hint so they probably belive in this solution too :-)
http://www.rooftopsolutions.nl/ Evert

Yes it is a bad idea, they may change it in a minor version. The documentation specifically mentions that.

If you use is_callable in the first line you’re safe, and users can still pass regular methods through the array(obj,method) syntax.
http://www.rooftopsolutions.nl/ Evert

Just saying, don’t promote bad practices on your blog, I care less what you do in your private code ^_^
Che

See alpha version of closure-based http://github.com/BreathLess/Codeine-NG
No fixed dependencies at all.
http://sznapka.pl wowo

wow, nice one! I’ll take a closer look at this in some evening. Thanks for the link

Wojciech Sznapka Blog – PHP / Symfony 2 / Open Source

Loosening dependencies with closures in PHP

Podobne wpisy

Language

Tags

Links

Latest posts

Latest comments

Author