How to declare a mutable string in ruby 2.3 && ruby 3

Question

I just pass into ruby 2.3 with the new frozen_string_literal option.

Over each of my file I add this line :

# frozen_string_literal: true

a = String('test')
a.frozen?        # true
a.gsub!('t', 'a') # raise error : OK

It work well but, is there a way to declare something like this :

a = MutableString('test')
a.frozen?        # false
a.gsub!('t', 'a') # aesa

Currently I make it work like this :

a = 'test'.dup
a.frozen?        # false
a.gsub!('t', 'a') # aesa

But it's a little bit ugly.

Answer 1

The elegant way to achieve this in future Ruby versions is still being discussed . Until then, of course, the best bet would therefore be to avoid it, or to indeed use String#dup explicitly.

Technically, however, there's nothing to stop you from doing something like this:

def MutableString(x)
  x.dup
end

MutableString('...')