Initialising instance variables to nil

[troessner]

Coming from here:

I'd consider initialising instance variables to nil is its own smell. There is no semantic difference between:

class Omg
  def initialize; @bar = nil; end
  def hola(arg); @bar = arg; end
end

and

class Omg
  def hola(arg); @bar = arg; end
end

I think initialising instance variables to nil is a strong hint that.....this shouldn't be an instance variable at all and we should give the user a corresponding suggestion.

WDYT?

[mvz]

Yes, I agree the initialization is irrelevant. I'm not sure what to suggest to the user though, apart from removing the line from the initializer. Perhaps at least adding a (private) reader, since that will absorb uninitialized ivar warnings.

[troessner]

How about suggesting to not make it an instance variable at all?

[mvz]

I think we need to be more specific about the alternatives then :smile:.

[troessner]

But thats what we have a /docs page for, dont we? We can then discuss examples there. We do the same thing for other more complex smells like FeatureEnvy.

[mvz]

Yes, I'm talking about what we should have in the docs.

[chastell]

(FWIW, as I was asked in the other issue: I do agree we should detect this smell and the discussion.) :)

[backus]

Could this awkwardly clash with the fact that ruby emits a warning if you access an ivar before it is initialized? It seems like this is usually the reason for @something = nil to live in initialize

[chastell]

Yes, probably – but I think @something = nil is a smell all the same, and the warning is just a symptom that could be dealt with in better ways (e.g., an @something ||= some_default accessor).