# File activesupport/lib/active_support/core_ext/enumerable.rb, line 218
def compact_blank
  reject(&:blank?)
end

Returns a new Array without the blank items. Uses Object#blank? for determining if an item is blank.

[1, "", nil, 2, " ", [], {}, false, true].compact_blank
# =>  [1, 2, true]

Set.new([nil, "", 1, 2])
# => [2, 1] (or [1, 2])

When called on a Hash, returns a new Hash without the blank values.

{ a: "", b: 1, c: nil, d: [], e: false, f: true }.compact_blank
# => { b: 1, f: true }

# File activesupport/lib/active_support/core_ext/enumerable.rb, line 152
def exclude?(object)
  !include?(object)
end

The negative of the Enumerable#include?. Returns true if the collection does not include the object.

# File activesupport/lib/active_support/core_ext/enumerable.rb, line 166
def excluding(*elements)
  elements.flatten!(1)
  reject { |element| elements.include?(element) }
end

Returns a copy of the enumerable excluding the specified elements.

["David", "Rafael", "Aaron", "Todd"].excluding "Aaron", "Todd"
# => ["David", "Rafael"]

["David", "Rafael", "Aaron", "Todd"].excluding %w[ Aaron Todd ]
# => ["David", "Rafael"]

{foo: 1, bar: 2, baz: 3}.excluding :bar
# => {foo: 1, baz: 3}

# File activesupport/lib/active_support/core_ext/enumerable.rb, line 230
def in_order_of(key, series)
  index_by(&key).values_at(*series).compact
end

Returns a new Array where the order has been set to that provided in the series, based on the key of the objects in the original enumerable.

[ Person.find(5), Person.find(3), Person.find(1) ].in_order_of(:id, [ 1, 5, 3 ])
# => [ Person.find(1), Person.find(5), Person.find(3) ]

If the series include keys that have no corresponding element in the Enumerable, these are ignored. If the Enumerable has additional elements that aren't named in the series, these are not included in the result.

# File activesupport/lib/active_support/core_ext/enumerable.rb, line 146
def including(*elements)
  to_a.including(*elements)
end

Returns a new array that includes the passed elements.

[ 1, 2, 3 ].including(4, 5)
# => [ 1, 2, 3, 4, 5 ]

["David", "Rafael"].including %w[ Aaron Todd ]
# => ["David", "Rafael", "Aaron", "Todd"]

# File activesupport/lib/active_support/core_ext/enumerable.rb, line 86
def index_by
  if block_given?
    result = {}
    each { |elem| result[yield(elem)] = elem }
    result
  else
    to_enum(:index_by) { size if respond_to?(:size) }
  end
end

Convert an enumerable to a hash, using the block result as the key and the element as the value.

people.index_by(&:login)
# => { "nextangle" => <Person ...>, "chade-" => <Person ...>, ...}

people.index_by { |person| "#{person.first_name} #{person.last_name}" }
# => { "Chade- Fowlersburg-e" => <Person ...>, "David Heinemeier Hansson" => <Person ...>, ...}

# File activesupport/lib/active_support/core_ext/enumerable.rb, line 109
def index_with(default = INDEX_WITH_DEFAULT)
  if block_given?
    result = {}
    each { |elem| result[elem] = yield(elem) }
    result
  elsif default != INDEX_WITH_DEFAULT
    result = {}
    each { |elem| result[elem] = default }
    result
  else
    to_enum(:index_with) { size if respond_to?(:size) }
  end
end

Convert an enumerable to a hash, using the element as the key and the block result as the value.

post = Post.new(title: "hey there", body: "what's up?")

%i( title body ).index_with { |attr_name| post.public_send(attr_name) }
# => { title: "hey there", body: "what's up?" }

If an argument is passed instead of a block, it will be used as the value for all elements:

%i( created_at updated_at ).index_with(Time.now)
# => { created_at: 2020-03-09 22:31:47, updated_at: 2020-03-09 22:31:47 }

# File activesupport/lib/active_support/core_ext/enumerable.rb, line 127
def many?
  cnt = 0
  if block_given?
    any? do |element|
      cnt += 1 if yield element
      cnt > 1
    end
  else
    any? { (cnt += 1) > 1 }
  end
end

Returns true if the enumerable has more than 1 element. Functionally equivalent to enum.to_a.size > 1. Can be called with a block too, much like any?, so people.many? { |p| p.age > 26 } returns true if more than one person is over 26.

# File activesupport/lib/active_support/core_ext/enumerable.rb, line 35
def maximum(key)
  map(&key).max
end

Calculates the maximum from the extracted elements.

payments = [Payment.new(5), Payment.new(15), Payment.new(10)]
payments.maximum(:price) # => 15

# File activesupport/lib/active_support/core_ext/enumerable.rb, line 27
def minimum(key)
  map(&key).min
end

Calculates the minimum from the extracted elements.

payments = [Payment.new(5), Payment.new(15), Payment.new(10)]
payments.minimum(:price) # => 5

# File activesupport/lib/active_support/core_ext/enumerable.rb, line 195
def pick(*keys)
  return if none?

  if keys.many?
    keys.map { |key| first[key] }
  else
    first[keys.first]
  end
end

Extract the given key from the first element in the enumerable.

[{ name: "David" }, { name: "Rafael" }, { name: "Aaron" }].pick(:name)
# => "David"

[{ id: 1, name: "David" }, { id: 2, name: "Rafael" }].pick(:id, :name)
# => [1, "David"]

# File activesupport/lib/active_support/core_ext/enumerable.rb, line 179
def pluck(*keys)
  if keys.many?
    map { |element| keys.map { |key| element[key] } }
  else
    key = keys.first
    map { |element| element[key] }
  end
end

Extract the given key from each element in the enumerable.

[{ name: "David" }, { name: "Rafael" }, { name: "Aaron" }].pluck(:name)
# => ["David", "Rafael", "Aaron"]

[{ id: 1, name: "David" }, { id: 2, name: "Rafael" }].pluck(:id, :name)
# => [[1, "David"], [2, "Rafael"]]

# File activesupport/lib/active_support/core_ext/enumerable.rb, line 240
def sole
  case count
  when 1   then return first # rubocop:disable Style/RedundantReturn
  when 0   then raise SoleItemExpectedError, "no item found"
  when 2.. then raise SoleItemExpectedError, "multiple items found"
  end
end

Returns the sole item in the enumerable. If there are no items, or more than one item, raises Enumerable::SoleItemExpectedError.

["x"].sole          # => "x"
Set.new.sole        # => Enumerable::SoleItemExpectedError: no item found
{ a: 1, b: 2 }.sole # => Enumerable::SoleItemExpectedError: multiple items found

# File activesupport/lib/active_support/core_ext/enumerable.rb, line 57
  def sum(identity = nil, &block)
    if identity
      _original_sum_with_required_identity(identity, &block)
    elsif block_given?
      map(&block).sum
    # we check `first(1) == []` to check if we have an
    # empty Enumerable; checking `empty?` would return
    # true for `[nil]`, which we want to deprecate to
    # keep consistent with Ruby
    elsif first.is_a?(Numeric) || first(1) == []
      identity ||= 0
      _original_sum_with_required_identity(identity, &block)
    else
      ActiveSupport::Deprecation.warn(<<-MSG.squish)
        Rails 7.0 has deprecated Enumerable.sum in favor of Ruby's native implementation available since 2.4.
        Sum of non-numeric elements requires an initial argument.
      MSG
      inject(:+) || 0
    end
  end

Calculates a sum from the elements.

payments.sum { |p| p.price * p.tax_rate }
payments.sum(&:price)

The latter is a shortcut for:

payments.inject(0) { |sum, p| sum + p.price }

It can also calculate the sum without the use of a block.

[5, 15, 10].sum # => 30
['foo', 'bar'].sum('') # => "foobar"
[[1, 2], [3, 1, 5]].sum([]) # => [1, 2, 3, 1, 5]

The default sum of an empty list is zero. You can override this default:

[].sum(Payment.new(0)) { |i| i.amount } # => Payment.new(0)