In many projects you can see code such as:
class Something before_validation :strip_title def strip_title self.title = title.strip end end
However there is different way to write this requirement.
class Something def title=(val) @title = val.strip end end
class Something def title=(val) self['title'] = val.strip end end
class Something def title=(val) super(val.strip) end end
…depending on the way you keep the data inside the class. Various gems use various ways.
Here is why I like it that way:
- it explodes when
nil. Yes, I consider it to be a good thing. Rarely my frontend can send
nilas title so when it happens most likely something would be broken and exception is OK. It won’t happen anyway. It’s just my programmer lizard brain telling me all corner cases. I like this part of the brain. But sometimes it deceives us and makes us focus on cases which won’t happen.
- It’s less magic. Rails validation callbacks are cool and I’ve used them many times. That said, I don’t need them to strip fuckin’ spaces.
- It works in more cases. It works when you read the field after setting it, without doing save in between. Or if you save without running the validations (for whatever reasons).
something.code = " 123 " something.code # => 123 something.save(validate: false)
I especially like to impose such cleaning rules on objects used for crossing boundaries such as Command or Form objects.
That’s it. That’s the entire, small lesson. If you want more, subscribe to our mailing list below or buy Fearless Refactoring.