Question

I have a Ruby hash that looks like this:

h = {"side1"=>["green", "Green"], "side2"=>["verde", "Verde"]}

How can I get the first (or last) item at a particular key in the hash?

Answer 1

Actually, your example pseudo code in your question is correct.

For your hash

h = {
   "side1" => ["green", "Green"], 
   "side2" => ["verde", "Verde"]
}

the keys are 'side1' and 'side2' (with their values right of the hashrocket)

So, h['side2'].first says that for the value of key 'side2', get the first element in the value ["verde", "Verde"], which is an array. h['side2'][0] would also work. the alias first is a convenience method.

To get the last element of an array without having to know how big it is, use a negative index. e.g. h['side2'][-1], which is equivalent to h['side2'][1] in this case.

Note that keys in a hash are particular about whether it is a string or symbol. That is h[:side2] would return nil, as the key hasn’t been set. Rails has a class HashWithIndifferentAccess that treats symbols and strings as equivalent keys.

EDIT

I should have mentioned that I tested my answer in irb. irb is a great way to test your ideas about what may and may not work. In your terminal prompt, type irb, enter, and play with ruby.