Symfony2 compiler pass with tags and custom attributes

It passed about half year since I scrat­ched Symfony2 Frame­work surface. Basics are behind me, now it’s time for middle-level stuff. I’m exci­ted to start a whole new Symfony rela­ted blog post series. I didn’t wanted to copy typi­cal tuto­rial topics. It would be waste of your time and my work. I thought it would be nice to show some code rela­ted to Symfony Depen­dency Injec­tion Conta­iner.

Tuto­rials usually show typi­cal conta­iner servi­ces defi­ni­tion. Boring stuff. I’m going to show you dyna­mic collec­tion of servi­ces passed into proces­sor service. The idea is that collec­tion doesn’t know its elements, so every bundle can define its own servi­ces to be added to collec­tion. The secret is tags. To add some spice, tagged service can be defi­ned with prio­rity. And we can specify that this proces­sor should be run at the begin­ning, and that at the end.

We’ll start with defi­ning common proces­sor inter­face and some basic imple­men­ta­tions.

Now it’s time for a service that proces­ses given argu­ment with all the proces­sors one by one.

We could define typi­cal conta­iner defi­ni­tions and pass proces­sors right into proces­sing service, but remem­ber about requ­ire­ment that exter­nal bundles can define their own proces­sors. We’ll use tags.

Now the key part: compi­ler pass defi­ni­tion.


At the first sight you may think that it’s a lot of logic to run to define stupid proces­sor. What about perfor­mance? No worries. Remem­ber, the compi­la­tion outcome is dumped into cache file on prod envi­ron­ment. All these fore­ach loops and prio­rity queues are being run only once.

Solu­tion is pretty gene­ric, you can easily adapt to your own needs. Of course code is on MIT license, so grab it and use in your own (even commer­cial) projects!

Happy PHP conta­iner compiling :-)


New Composer version constraints

Topic is not 0 day news. First commits adding new version constra­ints were added on decem­ber 2014. I’ll only mention what’s new:

  • when defi­ning logi­cal AND you can use space just like you use comma, so >1.0 <=1.5 is the same as >1.0,<=1.5
  • when defi­ning logi­cal OR you should (must?) use double pipe || instead of single pipe |
  • I’m sure you know tilde opera­tor ~1.5 (which means you’re inte­re­sted in versions >=1.5,<2), new caret opera­tor ^ was intro­du­ced, ^1.2.3 defi­ni­tion means >=1.2.3,<2, so the change is you can more preci­sely define star­ting version; if you would like to define the same constra­int without caret opera­tor you would need to write ~1.2,>=1.2.3, so new opera­tor is more concise
  • the last one, hyphen opera­tor - is inclu­sive set of versions, it’s a kind of myste­rious to me, 1.0 - 2.0 is equiva­lent to >=1.0.0 <2.1 and 1.0.0 - 2.1.0 is equiva­lent to >=1.0.0 <=2.1.0 (take a look at compo­ser doc and then matcher source code)

Roman Numerals Converter Code Kata summary

Brow­sing thro­ugh GitHub i came across XSolve Code Kata repo­si­tory. Code Kata #1 have two imple­men­ta­tions (PHP, C#) of Roman nume­rals conver­ter. I had some free time and wanted to imple­ment Scala version. The result is on my GitHub.

I added Roman-Arabic conver­sion compa­red to XSolve solu­tion. Project has full test cove­rage, what means every single line of code was execu­ted at least once (love that fancy Travis and Cove­ralls badges).

What is being used:

  • case clas­ses ArabicNum and RomanNum, of course it could be int and string, but hey, Scala has rich typesystem ;-)
  • whole NumConverter class is single­ton object
  • one pattern matching method
  • break() func­tions, which I find funny that Scala doesn’t have imple­men­ted such base things natively
  • FlatSpec from Scala­Test suite (BDD approach)

Be warned, vali­da­tion func­tion is ugly, conta­ins nested IFs and needs refac­to­ring, but as long as it passes tests it’s OK.

Whole code is not very „Scalish”. I consi­der myself as an Advan­ced Begin­ner on Scala accor­ding to Drey­fus Model and I don’t care ;-)