Wraps its argument in an array unless it is already an array (or array-like).

Specifically:

• If the argument is nil an empty list is returned.

• Otherwise, if the argument responds to to_ary it is invoked, and its result returned.

• Otherwise, returns an array with the argument as its single element.

  Array.wrap(nil)       # => []
  Array.wrap([1, 2, 3]) # => [1, 2, 3]
  Array.wrap(0)         # => [0]
  

This method is similar in purpose to Kernel#Array, but there are some differences:

• If the argument responds to to_ary the method is invoked. Kernel#Array moves on to try to_a if the returned value is nil, but Array.wrap returns nil right away.

• If the returned value from to_ary is neither nil nor an Array object, Kernel#Array raises an exception, while Array.wrap does not, it just returns the value.

• It does not call to_a on the argument, but returns an empty array if argument is nil.

The second point is easily explained with some enumerables:

Array(foo: :bar)      # => [[:foo, :bar]]
Array.wrap(foo: :bar) # => [{:foo=>:bar}]

There's also a related idiom that uses the splat operator:

[*object]

which returns [] for nil, but calls to Array(object) otherwise.

The differences with Kernel#Array explained above apply to the rest of objects.

# File activesupport/lib/active_support/core_ext/array/wrap.rb, line 36
def self.wrap(object)
  if object.nil?
    []
  elsif object.respond_to?(:to_ary)
    object.to_ary || [object]
  else
    [object]
  end
end

Returns a deep copy of array.

array = [1, [2, 3]]
dup   = array.deep_dup
dup[1][2] = 4

array[1][2] # => nil
dup[1][2]   # => 4

# File activesupport/lib/active_support/core_ext/object/deep_dup.rb, line 27
def deep_dup
  map { |it| it.deep_dup }
end

Extracts options from a set of arguments. Removes and returns the last element in the array if it's a hash, otherwise returns a blank hash.

def options(*args)
  args.extract_options!
end

options(1, 2)        # => {}
options(1, 2, a: :b) # => {:a=>:b}

# File activesupport/lib/active_support/core_ext/array/extract_options.rb, line 22
def extract_options!
  if last.is_a?(Hash) && last.extractable_options?
    pop
  else
    {}
  end
end

Equal to self[4].

%w( a b c d e ).fifth # => "e"

# File activesupport/lib/active_support/core_ext/array/access.rb, line 46
def fifth
  self[4]
end

Equal to self[41]. Also known as accessing “the reddit”.

(1..42).to_a.forty_two # => 42

# File activesupport/lib/active_support/core_ext/array/access.rb, line 53
def forty_two
  self[41]
end

Equal to self[3].

%w( a b c d e ).fourth # => "d"

# File activesupport/lib/active_support/core_ext/array/access.rb, line 39
def fourth
  self[3]
end

Returns the tail of the array from position.

%w( a b c d ).from(0)  # => ["a", "b", "c", "d"]
%w( a b c d ).from(2)  # => ["c", "d"]
%w( a b c d ).from(10) # => []
%w().from(0)           # => []

# File activesupport/lib/active_support/core_ext/array/access.rb, line 8
def from(position)
  self[position, length] || []
end

Splits or iterates over the array in number of groups, padding any remaining slots with fill_with unless it is false.

%w(1 2 3 4 5 6 7 8 9 10).in_groups(3) {|group| p group}
["1", "2", "3", "4"]
["5", "6", "7", nil]
["8", "9", "10", nil]

%w(1 2 3 4 5 6 7 8 9 10).in_groups(3, ' ') {|group| p group}
["1", "2", "3", "4"]
["5", "6", "7", " "]
["8", "9", "10", " "]

%w(1 2 3 4 5 6 7).in_groups(3, false) {|group| p group}
["1", "2", "3"]
["4", "5"]
["6", "7"]

# File activesupport/lib/active_support/core_ext/array/grouping.rb, line 55
def in_groups(number, fill_with = nil)
  # size.div number gives minor group size;
  # size % number gives how many objects need extra accommodation;
  # each group hold either division or division + 1 items.
  division = size.div number
  modulo = size % number

  # create a new array avoiding dup
  groups = []
  start = 0

  number.times do |index|
    length = division + (modulo > 0 && modulo > index ? 1 : 0)
    groups << last_group = slice(start, length)
    last_group << fill_with if fill_with != false &&
      modulo > 0 && length == division
    start += length
  end

  if block_given?
    groups.each { |g| yield(g) }
  else
    groups
  end
end

Splits or iterates over the array in groups of size number, padding any remaining slots with fill_with unless it is false.

%w(1 2 3 4 5 6 7 8 9 10).in_groups_of(3) {|group| p group}
["1", "2", "3"]
["4", "5", "6"]
["7", "8", "9"]
["10", nil, nil]

%w(1 2 3 4 5).in_groups_of(2, ' ') {|group| p group}
["1", "2"]
["3", "4"]
["5", " "]

%w(1 2 3 4 5).in_groups_of(2, false) {|group| p group}
["1", "2"]
["3", "4"]
["5"]

# File activesupport/lib/active_support/core_ext/array/grouping.rb, line 20
def in_groups_of(number, fill_with = nil)
  if fill_with == false
    collection = self
  else
    # size % number gives how many extra we have;
    # subtracting from number gives how many to add;
    # modulo number ensures we don't add group of just fill.
    padding = (number - size % number) % number
    collection = dup.concat(Array.new(padding, fill_with))
  end

  if block_given?
    collection.each_slice(number) { |slice| yield(slice) }
  else
    collection.each_slice(number).to_a
  end
end

Equal to self[1].

%w( a b c d e ).second # => "b"

# File activesupport/lib/active_support/core_ext/array/access.rb, line 25
def second
  self[1]
end

Divides the array into one or more subarrays based on a delimiting value or the result of an optional block.

[1, 2, 3, 4, 5].split(3)              # => [[1, 2], [4, 5]]
(1..10).to_a.split { |i| i % 3 == 0 } # => [[1, 2], [4, 5], [7, 8], [10]]

# File activesupport/lib/active_support/core_ext/array/grouping.rb, line 86
def split(value = nil)
  if block_given?
    inject([[]]) do |results, element|
      if yield(element)
        results << []
      else
        results.last << element
      end

      results
    end
  else
    results, arr = [[]], self.dup
    until arr.empty?
      if (idx = arr.index(value))
        results.last.concat(arr.shift(idx))
        arr.shift
        results << []
      else
        results.last.concat(arr.shift(arr.size))
      end
    end
    results
  end
end

Equal to self[2].

%w( a b c d e ).third # => "c"

# File activesupport/lib/active_support/core_ext/array/access.rb, line 32
def third
  self[2]
end

Returns the beginning of the array up to position.

%w( a b c d ).to(0)  # => ["a"]
%w( a b c d ).to(2)  # => ["a", "b", "c"]
%w( a b c d ).to(10) # => ["a", "b", "c", "d"]
%w().to(0)           # => []

# File activesupport/lib/active_support/core_ext/array/access.rb, line 18
def to(position)
  first position + 1
end

Extends Array#to_s to convert a collection of elements into a comma separated id list if :db argument is given as the format.

Blog.all.to_formatted_s(:db) # => "1,2,3"

# File activesupport/lib/active_support/core_ext/array/conversions.rb, line 89
def to_formatted_s(format = :default)
  case format
  when :db
    if empty?
      'null'
    else
      collect { |element| element.id }.join(',')
    end
  else
    to_default_s
  end
end

Calls to_param on all its elements and joins the result with slashes. This is used by url_for in Action Pack.

# File activesupport/lib/active_support/core_ext/object/to_query.rb, line 39
def to_param
  collect { |e| e.to_param }.join '/'
end

Converts an array into a string suitable for use as a URL query string, using the given key as the param name.

['Rails', 'coding'].to_query('hobbies') # => "hobbies%5B%5D=Rails&hobbies%5B%5D=coding"

# File activesupport/lib/active_support/core_ext/object/to_query.rb, line 47
def to_query(key)
  prefix = "#{key}[]"

  if empty?
    nil.to_query(prefix)
  else
    collect { |value| value.to_query(prefix) }.join '&'
  end
end

Converts the array to a comma-separated sentence where the last element is joined by the connector word.

You can pass the following options to change the default behavior. If you pass an option key that doesn't exist in the list below, it will raise an ArgumentError.

Options

• :words_connector - The sign or word used to join the elements in arrays with two or more elements (default: “, ”).

• :two_words_connector - The sign or word used to join the elements in arrays with two elements (default: “ and ”).

• :last_word_connector - The sign or word used to join the last element in arrays with three or more elements (default: “, and ”).

• :locale - If i18n is available, you can set a locale and use the connector options defined on the 'support.array' namespace in the corresponding dictionary file.

Examples

[].to_sentence                      # => ""
['one'].to_sentence                 # => "one"
['one', 'two'].to_sentence          # => "one and two"
['one', 'two', 'three'].to_sentence # => "one, two, and three"

['one', 'two'].to_sentence(passing: 'invalid option')
# => ArgumentError: Unknown key :passing

['one', 'two'].to_sentence(two_words_connector: '-')
# => "one-two"

['one', 'two', 'three'].to_sentence(words_connector: ' or ', last_word_connector: ' or at least ')
# => "one or two or at least three"

Using :locale option:

# Given this locale dictionary:
#
#   es:
#     support:
#       array:
#         words_connector: " o "
#         two_words_connector: " y "
#         last_word_connector: " o al menos "

['uno', 'dos'].to_sentence(locale: :es)
# => "uno y dos"

['uno', 'dos', 'tres'].to_sentence(locale: :es)
# => "uno o dos o al menos tres"

# File activesupport/lib/active_support/core_ext/array/conversions.rb, line 59
def to_sentence(options = {})
  options.assert_valid_keys(:words_connector, :two_words_connector, :last_word_connector, :locale)

  default_connectors = {
    :words_connector     => ', ',
    :two_words_connector => ' and ',
    :last_word_connector => ', and '
  }
  if defined?(I18n)
    i18n_connectors = I18n.translate(:'support.array', locale: options[:locale], default: {})
    default_connectors.merge!(i18n_connectors)
  end
  options = default_connectors.merge!(options)

  case length
  when 0
    ''
  when 1
    self[0].to_s.dup
  when 2
    "#{self[0]}#{options[:two_words_connector]}#{self[1]}"
  else
    "#{self[0...-1].join(options[:words_connector])}#{options[:last_word_connector]}#{self[-1]}"
  end
end

Returns a string that represents the array in XML by invoking to_xml on each element. Active Record collections delegate their representation in XML to this method.

All elements are expected to respond to to_xml, if any of them does not then an exception is raised.

The root node reflects the class name of the first element in plural if all elements belong to the same type and that's not Hash:

customer.projects.to_xml

<?xml version="1.0" encoding="UTF-8"?>
<projects type="array">
  <project>
    <amount type="decimal">20000.0</amount>
    <customer-id type="integer">1567</customer-id>
    <deal-date type="date">2008-04-09</deal-date>
    ...
  </project>
  <project>
    <amount type="decimal">57230.0</amount>
    <customer-id type="integer">1567</customer-id>
    <deal-date type="date">2008-04-15</deal-date>
    ...
  </project>
</projects>

Otherwise the root element is “objects”:

[{ foo: 1, bar: 2}, { baz: 3}].to_xml

<?xml version="1.0" encoding="UTF-8"?>
<objects type="array">
  <object>
    <bar type="integer">2</bar>
    <foo type="integer">1</foo>
  </object>
  <object>
    <baz type="integer">3</baz>
  </object>
</objects>

If the collection is empty the root element is “nil-classes” by default:

[].to_xml

<?xml version="1.0" encoding="UTF-8"?>
<nil-classes type="array"/>

To ensure a meaningful root element use the :root option:

customer_with_no_projects.projects.to_xml(root: 'projects')

<?xml version="1.0" encoding="UTF-8"?>
<projects type="array"/>

By default name of the node for the children of root is root.singularize. You can change it with the :children option.

The options hash is passed downwards:

Message.all.to_xml(skip_types: true)

<?xml version="1.0" encoding="UTF-8"?>
<messages>
  <message>
    <created-at>2008-03-07T09:58:18+01:00</created-at>
    <id>1</id>
    <name>1</name>
    <updated-at>2008-03-07T09:58:18+01:00</updated-at>
    <user-id>1</user-id>
  </message>
</messages>

# File activesupport/lib/active_support/core_ext/array/conversions.rb, line 179
def to_xml(options = {})
  require 'active_support/builder' unless defined?(Builder)

  options = options.dup
  options[:indent]  ||= 2
  options[:builder] ||= Builder::XmlMarkup.new(indent: options[:indent])
  options[:root]    ||=        if first.class != Hash && all? { |e| e.is_a?(first.class) }
      underscored = ActiveSupport::Inflector.underscore(first.class.name)
      ActiveSupport::Inflector.pluralize(underscored).tr('/', '_')
    else
      'objects'
    end

  builder = options[:builder]
  builder.instruct! unless options.delete(:skip_instruct)

  root = ActiveSupport::XmlMini.rename_key(options[:root].to_s, options)
  children = options.delete(:children) || root.singularize
  attributes = options[:skip_types] ? {} : { type: 'array' }

  if empty?
    builder.tag!(root, attributes)
  else
    builder.tag!(root, attributes) do
      each { |value| ActiveSupport::XmlMini.to_tag(children, value, options) }
      yield builder if block_given?
    end
  end
end