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Enumerable#max

Updated March 31, 2026 · Enumerable
ruby enumerable max maximum stdlib

Enumerable#max

The max method returns the largest element in an enumerable collection. It compares elements using the <=> operator (spaceship operator) to determine order.

Basic Usage

Without arguments, max returns the single largest element:

[3, 1, 4, 1, 5, 9, 2, 6].max
# => 9

["banana", "apple", "cherry"].max
# => "cherry"

Getting the N Largest Elements

Pass an integer n to get the n largest elements as an array:

[3, 1, 4, 1, 5, 9, 2, 6].max(3)
# => [9, 6, 5]

["banana", "apple", "cherry", "date"].max(2)
# => ["date", "cherry"]

Custom Comparison with a Block

You can provide a block to define custom comparison logic:

[-5, 3, -1, 7, -2].max { |a, b| a.abs <=> b.abs }
# => 7

["hello", "world", "ruby"].max { |a, b| a.length <=> b.length }
# => "hello"

The block must return -1, 0, or 1 (using the spaceship operator convention).

Handling Empty Collections

max returns nil when called on an empty collection:

[].max
# => nil

[].max(2)
# => []

max vs max_by

These two methods are often confused but behave differently:

MethodWhat it compares
maxCompares elements by their actual value using <=>
max_byCompares elements by the result of the block
# max compares by value
[1, 2, 3].max
# => 3

# max_by compares by block result
["one", "two", "three"].max_by { |s| s.length }
# => "three"

Practical Examples

Finding the Highest Price

products = [
  { name: "Widget", price: 29.99 },
  { name: "Gadget", price: 49.99 },
  { name: "Doohickey", price: 19.99 }
]

expensive = products.max { |a, b| a[:price] <=> b[:price] }
expensive[:name]
# => "Gadget"

Finding the Longest String

words = ["elephant", "cat", "giraffe", "ant"]

longest = words.max { |a, b| a.length <=> b.length }
# => "giraffe"

Getting the N Most Expensive Items

products = [
  { name: "Widget", price: 29.99 },
  { name: "Gadget", price: 49.99 },
  { name: "Doohickey", price: 19.99 },
  { name: "Thingamajig", price: 39.99 }
]

products.max(2) { |a, b| a[:price] <=> b[:price] }
# => [{:name=>"Gadget", :price=>49.99}, {:name=>"Thingamajig", :price=>39.99}]

Working with Custom Objects

class Player
  attr_reader :score

  def initialize(name, score)
    @name = name
    @score = score
  end

  def <=>(other)
    @score <=> other.score
  end

  def to_s
    @name
  end
end

players = [
  Player.new("Alice", 95),
  Player.new("Bob", 87),
  Player.new("Charlie", 92)
]

players.max
# => Alice (score: 95)

Performance Notes

max uses the <=> operator to compare elements. For arrays, it performs a single pass through the collection — O(n) time complexity.

When using max with a block, the comparison logic runs multiple times during the sort. For finding a single maximum, max_by is often more efficient since it only evaluates the block once per element.

See Also