Get the first item out of a Ruby array in a hash

I have a Ruby hash that looks like this:

h = {"side1"=>["开发者_StackOverflowgreen", "Green"], "side2"=>["verde", "Verde"]}

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

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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.

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I ran into a similar situation where I arbitrarily wanted the "first" entry from the hash for some test code. That's not exactly what this question is about, but it came up in the search I ran so figure it might do likewise for others.

Of course "first item" is arbitrary in a hash, but the keys method will return a list of all keys sorted by some magic. If you like that sort order, then you can get the "first" method with

h[h.keys.first]

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Any hash has keys and values you can simply make

hash.values.first
hash.values.last
hash.keys.first
hash.keys.last

So you will have the array of values you want in case first or last

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Yes. puts h["side2"].first should work. I guess this goes to show that Ruby follows the principle of least-surprise, where your pseudo-code turned out to be the same as the actual code. :-)