How symbols equal each others?

Question

When I do :symbol == :symbol I find that its true. They are the same.

If this is the case, how can we create arrays like this:

a = [{:name=>"Michael"},{:name=>"John"}]

Answer 1

Look the below code :

a = [{:name=>"Michael"},{:name=>"John"}]
a.map(&:object_id) # => [70992070, 70992050]

This is because a is an array of Hash, but they are 2 different hash objects. In Ruby, Hash must have uniq key. But 2 different hash can have same named symbols as keys.

Answer 2

You seem to be confused about hash keys. One hash cannot contain the same key twice, but two different hashes can have the same object as a key. For example:

a_key = "hello"
spanish = { a_key => "hola" }
french = { a_key => "bonjour" }
some_array = [spanish, french]

On top of that, it is possible for arrays to contain duplicate objects (e.g. [1, 2, 1] is valid) -- but these aren't even duplicates. Two hashes that contain the same key are still different objects.

There's nothing at all unusual about an array like that. In fact, it's normal for hashes in an array to have keys in common, because usually if you want to put things in an array, it means they have something in common that you can use to deal with them in the same way.