user-tap-example.rb

class User
  attr_accessor :first_name, :last_name
end

# sem o método tap

user = User.new
user.first_name = "Rodrigo"
user.last_name = "Pinto"

puts user.first_name # => Rodrigo
puts user.last_name # => Pinto

# com o método tap

user_using_tap = User.new.tap do |u|
  u.first_name = "Rodrigo 2"
  u.last_name = "Pinto 2"
end

puts user_using_tap.first_name # => Rodrigo 2
puts user_using_tap.last_name # => Pinto 2