Ruby has no constant values?

Question

It's possible to write this way

class Foo
 MY_CONST = 100
end

and it's also possible to change it Foo::MY_CONST = 123

There will be a warning from a Ruby compiler, but anyway a constant will be changed.

So Ruby has no constant values?

Indirectly related - http://stackoverflow.com/questions/2441524/closest-ruby-representation-of-a-private-static-final-and-public-static-final#2442640 — dfb, Aug 29 '12 at 15:44

score 2 · Accepted Answer · answered Aug 29 '12 at 17:41

it depends what kind of action you want to do with your constants.

If you have an

ARRAY = [1,2,3]
#and then 
ARRAY << 4

Ruby won't complain.

However, if you

ARRAY = [1,2,3].freeze
#and
ARRAY << 4
#RuntimeError: can't modify frozen Array

You can still

ARRAY = [1,2,3,4]
#warning: already initialized constant ARRAY

score 1 · Answer 2 · answered Aug 29 '12 at 23:31

1

If you freeze FOO, then trying to reassign FOO::MY_CONST will create a RuntimeError.

class FOO
  MY_CONST = 100
end

FOO.freeze
FOO::MY_CONST = 123

gives

RuntimeError: can't modify frozen Class

answered Aug 29 '12 at 23:31

Andrew Grimm

score 0 · Answer 3 · answered Aug 29 '12 at 16:11

0

They are semantically constants, so you can expect people not to change them. I'd call them liberal constants, see http://pastie.org/4608297

answered Aug 29 '12 at 16:11

Reactormonk

2

They can be changed. Even if people might not want to change them. – Aug 29 '12 at 16:18

3 Answers3