Question

I’m thinking about global variables in my rails application. I’ve searched the net about that, and found it (of course) flagged as a bad practice. I already knew that.

But I have not found another way than a global variable for what I need. Can an experienced Rails programmer help me ?

What I want to do is to create a new dedicated logger, for example logging to “log/audit.txt” and share it between several controllers. Of course, I would rather not have to recreate this “logger” object for every request.

For now, I create a logger in a global variable $my_logger in an initializer, and use it across my controllers.

What do you think ? Is there a better way to do that ?

Thank you.

Answer 1

The general OO stance against using global variables and singletons of any type — in Rails and in all other OO habitats — is to avoid the “slippery slope” towards not doing OO design at all. Global variables are to be avoided as much as possible, but your logger is obviously a case where a Singleton of some sort makes sense. The Rails environment is an example: you only have on Rails environment per application, and it’s essentially a Singleton. Or consider Notifier.deliver…

Don’t worry about where to put it if it must be global. Make a Singleton object with class methods as accessors and put it in lib or anywhere you think is appropriate (making a plugin might also be appropriate, for instance). Then you just use Logger.instance.log whatever. Of course you’ll have to put in safeguards to make sure that the thing gets instantiated only once.