How to Filter an Array in Ruby

1. Filter an Array Using the select Method in Ruby
2. Filter an Array Using the reject Method in Ruby
3. Filter an Array Using the inject Method in Ruby

The following topic is the methods used to filter an array in Ruby.

Filter an Array Using the select Method in Ruby

This is a very common method of filtering in Ruby. It’s useful when selecting a few elements from the array.

letters = %w[A k L B n O P c r]
small_letters = letters.select { |l| l == l.downcase }
puts small_letters

Output:

k
n
c
r

Filter an Array Using the reject Method in Ruby

This is the opposite of select. The ’ reject ’ method is preferred when many elements are taken from an array.

letters = %w[A k L B n O P C r]
small_letters = letters.reject { |l| l != l.downcase }
puts small_letters

Output:

k
n
r

Filter an Array Using the inject Method in Ruby

The inject method is usually used to accumulate all the elements of an array but can filter by setting the initial accumulator to an empty array.

letters = %w[A k L B n O P c r]
small_letters = letters.each_with_object([]) do |l, result|
  result << l if l == l.downcase
end
puts small_letters

Output:

k
n
q
r