Methods
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Class Public methods
wrap(object)

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

Specifically:

  • If the argument is nilan empty list is returned.

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

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

    ::wrap # => [] ::wrap([1, 2, 3]) # => [1, 2, 3] ::wrap # => [0]

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

  • If the argument responds to to_arythe method is invoked. Kernel#Array

moves on to try to_aif the returned value is nil, but Array.wrapreturns such a nilright away.

  • If the returned value from to_aryis neither nil nor an Arrayobject, Kernel#Array

raises an exception, while Array.wrapdoes not, it just returns the value.

  • It does not call to_aon the argument, though special-cases nilto return an empty array.

The last point is particularly worth comparing for some enumerables:

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

Array("foo\nbar")        # => ["foo\n", "bar"], in Ruby 1.8
Array.wrap("foo\nbar")   # => ["foo\nbar"]

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

[*object]

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

Thus, in this case the behavior is different for nil, and the differences with Kernel#Arrayexplained above apply to the rest of +object+s.

# File activesupport/lib/active_support/core_ext/array/wrap.rb, line 39
def self.wrap(object)
  if object.nil?
    []
  elsif object.respond_to?(:to_ary)
    object.to_ary || [object]
  else
    [object]
  end
end
Instance Public methods
extract_options!()

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
fifth()

Equal to self[4].

# File activesupport/lib/active_support/core_ext/array/access.rb, line 38
def fifth
  self[4]
end
forty_two()

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

# File activesupport/lib/active_support/core_ext/array/access.rb, line 43
def forty_two
  self[41]
end
fourth()

Equal to self[3].

# File activesupport/lib/active_support/core_ext/array/access.rb, line 33
def fourth
  self[3]
end
from(position)

Returns the tail of the array from position.

%w( a b c d ).from(0)  # => %w( a b c d )
%w( a b c d ).from(2)  # => %w( c d )
%w( a b c d ).from(10) # => %w()
%w().from(0)           # => %w()
# File activesupport/lib/active_support/core_ext/array/access.rb, line 8
def from(position)
  self[position, length] || []
end
in_groups(number, fill_with = nil)

Splits or iterates over the array in numberof groups, padding any remaining slots with fill_withunless 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).in_groups(3, ' ') {|group| p group}
["1", "2", "3"]
["4", "5", " "]
["6", "7", " "]

%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 56
def in_groups(number, fill_with = nil)
  # size / 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 / 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)
    padding = fill_with != false &&
      modulo > 0 && length == division ? 1 : 0
    groups << slice(start, length).concat([fill_with] * padding)
    start += length
  end

  if block_given?
    groups.each { |g| yield(g) }
  else
    groups
  end
end
in_groups_of(number, fill_with = nil)

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

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

%w(1 2 3).in_groups_of(2, '&nbsp;') {|group| p group}
["1", "2"]
["3", "&nbsp;"]

%w(1 2 3).in_groups_of(2, false) {|group| p group}
["1", "2"]
["3"]
# File activesupport/lib/active_support/core_ext/array/grouping.rb, line 19
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([fill_with] * padding)
  end

  if block_given?
    collection.each_slice(number) { |slice| yield(slice) }
  else
    groups = []
    collection.each_slice(number) { |group| groups << group }
    groups
  end
end
sample(n=nil)

Backport of #sample based on Marc-Andre Lafortune's github.com/marcandre/backports/ Returns a random element or nrandom elements from the array. If the array is empty and nis nil, returns nil. If nis passed and its value is less than 0, it raises an ArgumentErrorexception. If the value of nis equal or greater than 0 it returns [].

[1,2,3,4,5,6].sample     # => 4
[1,2,3,4,5,6].sample(3)  # => [2, 4, 5]
[1,2,3,4,5,6].sample(-3) # => ArgumentError: negative array size
           [].sample     # => nil
           [].sample(3)  # => []
# File activesupport/lib/active_support/core_ext/array/random_access.rb, line 13
def sample(n=nil)
  return self[Kernel.rand(size)] if n.nil?
  n = n.to_int
rescue Exception => e
  raise TypeError, "Coercion error: #{n.inspect}.to_int => Integer failed:\n(#{e.message})"
else
  raise TypeError, "Coercion error: obj.to_int did NOT return an Integer (was #{n.class})" unless n.kind_of? Integer
  raise ArgumentError, "negative array size" if n < 0
  n = size if n > size
  result = Array.new(self)
  n.times do |i|
    r = i + Kernel.rand(size - i)
    result[i], result[r] = result[r], result[i]
  end
  result[n..size] = []
  result
end
second()

Equal to self[1].

# File activesupport/lib/active_support/core_ext/array/access.rb, line 23
def second
  self[1]
end
split(value = nil)

Divides the array into one or more subarrays based on a delimiting valueor 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 87
def split(value = nil)
  using_block = block_given?

  inject([[]]) do |results, element|
    if (using_block && yield(element)) || (value == element)
      results << []
    else
      results.last << element
    end

    results
  end
end
third()

Equal to self[2].

# File activesupport/lib/active_support/core_ext/array/access.rb, line 28
def third
  self[2]
end
to(position)

Returns the beginning of the array up to position.

%w( a b c d ).to(0)  # => %w( a )
%w( a b c d ).to(2)  # => %w( a b c )
%w( a b c d ).to(10) # => %w( a b c d )
%w().to(0)           # => %w()
# File activesupport/lib/active_support/core_ext/array/access.rb, line 18
def to(position)
  self.first position + 1
end
to_default_s(format = :default)
Alias for: to_s
to_formatted_s(format = :default)

Converts a collection of elements into a formatted string by calling to_son all elements and joining them:

Blog.all.to_formatted_s # => "First PostSecond PostThird Post"

Adding in the :dbargument as the format yields a comma separated id list:

Blog.all.to_formatted_s(:db) # => "1,2,3"
Also aliased as: to_s
# File activesupport/lib/active_support/core_ext/array/conversions.rb, line 46
def to_formatted_s(format = :default)
  case format
    when :db
      if respond_to?(:empty?) && self.empty?
        "null"
      else
        collect { |element| element.id }.join(",")
      end
    else
      to_default_s
  end
end
to_param()

Calls to_paramon all its elements and joins the result with slashes. This is used by url_forin Action Pack.

# File activesupport/lib/active_support/core_ext/object/to_param.rb, line 29
def to_param
  collect { |e| e.to_param }.join '/'
end
to_query(key)

Converts an array into a string suitable for use as a URL query string, using the given keyas 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 19
def to_query(key)
  prefix = "#{key}[]"
  collect { |value| value.to_query(prefix) }.join '&'
end
to_s(format = :default)
Also aliased as: to_default_s
Alias for: to_formatted_s
to_sentence(options = {})

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

# File activesupport/lib/active_support/core_ext/array/conversions.rb, line 11
def to_sentence(options = {})
  if defined?(I18n)
    default_words_connector     = I18n.translate(:'support.array.words_connector',     :locale => options[:locale])
    default_two_words_connector = I18n.translate(:'support.array.two_words_connector', :locale => options[:locale])
    default_last_word_connector = I18n.translate(:'support.array.last_word_connector', :locale => options[:locale])
  else
    default_words_connector     = ", "
    default_two_words_connector = " and "
    default_last_word_connector = ", and "
  end

  options.assert_valid_keys(:words_connector, :two_words_connector, :last_word_connector, :locale)
  options.reverse_merge! :words_connector => default_words_connector, :two_words_connector => default_two_words_connector, :last_word_connector => default_last_word_connector

  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
to_xml(options = {})

Returns a string that represents the array in XML by invoking to_xmlon 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 “records”:

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

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

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 :rootoption:

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 :childrenoption.

The optionshash 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 136
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.to_s != "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"}
  return builder.tag!(root, attributes) if empty?

  builder.__send__(:method_missing, root, attributes) do
    each { |value| ActiveSupport::XmlMini.to_tag(children, value, options) }
    yield builder if block_given?
  end
end
uniq_by()

Returns an unique array based on the criteria given as a Proc.

[1, 2, 3, 4].uniq_by { |i| i.odd? } # => [1, 2]
# File activesupport/lib/active_support/core_ext/array/uniq_by.rb, line 6
def uniq_by
  hash, array = {}, []
  each { |i| hash[yield(i)] ||= (array << i) }
  array
end
uniq_by!()

Same as #uniq_by, but modifies self.

# File activesupport/lib/active_support/core_ext/array/uniq_by.rb, line 13
def uniq_by!
  replace(uniq_by{ |i| yield(i) })
end