A Quick Guide to Ruby's tally Method

Ruby 2.7 introduced a small but powerful method: tally. If you’ve ever written code to count how many times each item appears in a collection, you’re going to love this.

What Is tally?

The tally method is available on any object that includes Enumerable, like arrays. It returns a hash where the keys are the unique elements from the collection, and the values are the number of times each element appears.

A Basic Example

Here’s how you’d use tally in a typical scenario:

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["apple", "banana", "apple", "orange", "banana", "apple"].tally
# => {"apple"=>3, "banana"=>2, "orange"=>1}

No loops, no manual hashes — just one clean, readable line.

Without tally: The Old Way

Before tally, counting occurrences looked more like this:

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counts = Hash.new(0)
["apple", "banana", "apple"].each do |fruit|
  counts[fruit] += 1
end
# => {"apple"=>2, "banana"=>1}

It works fine, but tally makes this common pattern much more concise.

Use Cases for tally

Here are a few situations where tally shines:

Counting votes

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votes = ["yes", "no", "yes", "yes", "no"]
votes.tally
# => {"yes"=>3, "no"=>2}

Word frequencies

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sentence = "the quick brown fox jumps over the lazy dog"
words = sentence.split
words.tally
# => {"the"=>2, "quick"=>1, "brown"=>1, ...}

Grouping errors or statuses

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statuses = [:ok, :ok, :error, :timeout, :ok, :error]
statuses.tally
# => {:ok=>3, :error=>2, :timeout=>1}

Things to Keep in Mind

• tally works only on Enumerables (like arrays). It doesn’t exist for plain hashes.
• It returns a new hash; the original array is unchanged.
• If you need weighted tallies or conditional logic, you might still need custom logic — but for simple counts, tally is perfect.

Ruby’s tally method is a great example of how the language evolves to make code more expressive and elegant. It replaces a common multi-line pattern with a single readable line, and once you start using it, you’ll likely reach for it often.