Can I use methods instead of constants?

Question

Is there any point of using constants instead of methods returning those constants like this?

class Foo
  LETTERS = [:a, :b, :c]
  # and them call it Foo::LETTERS
end

# or 
class Foo
  def self.letters
    [:a, :b, :c]
    # and then call it Foo.letters, more simplier
  end
end

I could see only one advantage of first approach: warning when trying to redefine constant, but it's rare case, I think.

The second approach creates a new array each time you call `Foo.letters`... — Uri Agassi, May 18 '14 at 11:20
As per your current context, I think first approach is good, if you don't have in mind to return a different array object in each access to `LETTERS`. — Arup Rakshit, May 18 '14 at 11:22
oh, of course @UriAgassi is right. I forgot such a simple thing :( — hedgesky, May 18 '14 at 11:27

score 5 · Accepted Answer · edited May 23 '17 at 12:23

Your second approach creates a new array each time the method Foo.letters is called. This, of course, can be fixed by saving the value:

class Foo
  def self.letters
    @letters ||= [:a, :b, :c]
  end
end

Also, there are some changes in behavior when inheriting such a class with each approach (see "How to use an overridden constant in an inheritanced class")

Personally, I don't see how Foo.letters is simpler than Foo::LETTERS - an extra character? I think that constants should be used for constants, and that static methods have their own use-cases...

Can I use methods instead of constants?

1 Answers1