Lighthouse Labs W1D3: The Power of Symbols

// Apr 1, 2015

After programming in Ruby for about 2 good months I am ashamed to say that I had no idea just how powerful symbols were!

When you create a string called "Johnny", it’ll have an object_id of 1. However once I create another identical string called "Johnny", that second string will have an object_id of 2.

This happens because no matter if the two strings are identical or not, they’re both recognized in the project as two different objects, causing them to have different Object IDs.

However, when you create a symbol called :johnny, i’ll have an object_id of 1. Yet, anywhere else in the program if I write another :johnny symbol, it’ll also have an object_id of 1. Each symbol is UNIQUE and cannot be changed.

So why should you care?

  1. This saves ALOT of memory. By using symbols in hashes as keys instead of strings, you’re not having to set a new object every time you change a key-pair value.

  2. Symbols can act as ID holders. Because symbols with the same name have the same object_id, you could use symbols to match truthiness. For example. When users input their hometown, I can call to_sym on that string. This would change "vancouver" to :vancouver. Then I can call Users.all(where hometown: :vancouver). Even though this symbol holds no real value, it is finding all the users that contains it’s object_id.

  3. Symbols themselves only contain a name and an Object ID and holds no real value unless assigned a value as a key-value pair in a hash. Therefore setting a variable such as city = :vancouver could mean that :vancouver is acting as an ID holder to match somewhere else OR :vancouver is actually the key to a value set elsewhere in your program!


Symbols are fucking amazing. I’m going to abuse their power for my own gain from now on and so should you.