Constant Assignment Bug in Ruby?

Question

We caught some code in Ruby that seems odd, and I was wondering if someone could explain it:

$ irb
irb(main):001:0> APPLE = 'aaa'
=> "aaa"
irb(main):002:0> banana = APPLE
=> "aaa"
irb(main):003:0> banana << 'bbb'
=> "aaabbb"
irb(main):004:0> banana
=> "aaabbb"
irb(main):005:0> APPLE
=> "aaabbb"

Catch that? The constant was appended to at the same time the local variable was.

Known behavior? Expected?

Answer 1

Known behaviour. Constants don't mean that you can't modify the object it refers to, merely that it'll give you a warning (and only a warning) if you assign it to a different object.

In short, ruby constants aren't.

Note: This behaviour is listed in an answer to "What are the Ruby Gotchas a newbie should be warned about?" It's a worthwhile read.