How to Sample a Random Element from Array in Ruby

In Ruby, you can sample a random element from an array using the sample method. For example, array.sample returns one random element from array. This method is simple and built-in for arrays.

Syntax

The sample method is called on an array to get random elements.

• array.sample: Returns one random element.
• array.sample(n): Returns an array of n unique random elements.

This method does not change the original array.

ruby

array.sample
array.sample(n)

Example

This example shows how to get one random element and multiple random elements from an array.

ruby

fruits = ['apple', 'banana', 'cherry', 'date', 'elderberry']

# Get one random fruit
random_fruit = fruits.sample
puts "Random fruit: #{random_fruit}"

# Get three unique random fruits
random_fruits = fruits.sample(3)
puts "Three random fruits: #{random_fruits.join(', ')}"

Output

Random fruit: banana
Three random fruits: cherry, apple, date

Common Pitfalls

Some common mistakes when sampling from arrays include:

• Using sample(n) with n larger than the array size, which returns fewer elements without error.
• Expecting sample to modify the original array; it does not.
• Using rand with array indexing manually, which is more complex and error-prone.

ruby

arr = [1, 2, 3]

# Wrong: asking for more elements than exist
puts arr.sample(5) # returns all elements without error, but fewer than 5

# Right: check size before sampling
n = 5
sampled = arr.sample([n, arr.size].min)
puts sampled

Output

[1, 2, 3]
[1, 2, 3]

Quick Reference

Method	Description	Example
array.sample	Returns one random element	['a', 'b', 'c'].sample # => 'b'
array.sample(n)	Returns an array of n unique random elements	['a', 'b', 'c'].sample(2) # => ['c', 'a']
array.sample(0)	Returns an empty array	['a', 'b'].sample(0) # => []

Key Takeaways

Use array.sample to get one random element from an array.

Use array.sample(n) to get multiple unique random elements.

sample does not change the original array.

Avoid requesting more elements than the array size with sample(n).

Using sample is simpler and safer than manual random indexing.