Changing multidimensional hash value and it's still equal

Question

I'm trying to update a multidimensinal hash and then compare the new hash with the old one, but no matter what value I change they still show up as equal. Is there an efficient way to compare every value in two hashes and return false if one isn't true

hash1 = {foo: {bar: "baz"}}
hash2 = hash1
hash2[:foo][:bar] = "foz"
hash2 == hash1 # This should be false but is returning true

They're the same object. Altering `hash2` alters `hash1`. If they were actually different, they would not show as equal. — khelwood, Sep 27 '19 at 17:32
Sounds like you need a [deep copy](https://en.wikipedia.org/wiki/Object_copying#Deep_copy), see https://stackoverflow.com/a/4157635/2166798 — pjs, Sep 27 '19 at 17:40

score 0 · Answer 1 · answered Sep 28 '19 at 11:13

Unlike assigning to simple primitive objects like integers, when you assign a variable to a hash, it will point to the same hash object. So, hash2 is pointing on the same object as hash1 in memory. If you need them to be structurally the same but are different objects, you need to copy the first hash deeply.

def deep_copy(hash)
  Marshal.load(Marshal.dump(hash))
end

hash1 = {foo: {bar: "baz"}}
hash2 = deep_copy(hash1)
hash2[:foo][:bar] = "foz"
hash2 == hash1

Changing multidimensional hash value and it's still equal

1 Answers1