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 - stackoverflow.com/questions/2441524/… — dfb
– dfb, Commented Aug 29, 2012 at 15:44

three · Accepted Answer · 2012-08-29 17:41:21Z

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

Andrew Grimm · Accepted Answer · 2012-08-29 23:31:07Z

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

Reactormonk · Accepted Answer · 2012-08-29 16:11:03Z

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, 2012 at 16:11

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1 Comment

They can be changed. Even if people might not want to change them.