How to understand symbols in Ruby

I was able to grock symbols when I thought of it like this. A Ruby string is an object that has a bunch of methods and properties. People like to use strings for keys, and when the string is used for a key then all those extra methods aren't used. So they made symbols, which are string objects with all the functionality removed, except that which is needed for it to be a good key.

Just think of symbols as constant strings.

Consider this:

x = :sym
y = :sym
(x.__id__ == y.__id__ ) && ( :sym.__id__ == x.__id__) # => true

x = "string"
y = "string"
(x.__id__ == y.__id__ ) || ( "string".__id__ == x.__id__) # => false

So, however you create a symbol object, as long as its contents are the same, it will refer to the same object in memory. This is not a problem because a symbol is an immutable object. Strings are mutable.

---

(In response to the comment below)

In the original article, the value is not being stored in a symbol, it is being stored in a hash. Consider this:

hash1 = { "string" => "value"}
hash2 = { "string" => "value"}

This creates six objects in the memory -- four string objects and two hash objects.

hash1 = { :symbol => "value"}
hash2 = { :symbol => "value"}

This only creates five objects in memory -- one symbol, two strings and two hash objects.