class Hash

# File activesupport/lib/active_support/core_ext/hash/conversions.rb, line 134
def from_trusted_xml(xml)
  from_xml xml, []
end

Builds a Hash from XML just like Hash.from_xml, but also allows Symbol and YAML.

# File activesupport/lib/active_support/core_ext/hash/conversions.rb, line 129
def from_xml(xml, disallowed_types = nil)
  ActiveSupport::XMLConverter.new(xml, disallowed_types).to_h
end

Returns a Hash containing a collection of pairs when the key is the node name and the value is its content

xml = <<-XML
  <?xml version="1.0" encoding="UTF-8"?>
    <hash>
      <foo type="integer">1</foo>
      <bar type="integer">2</bar>
    </hash>
XML

hash = Hash.from_xml(xml)
# => {"hash"=>{"foo"=>1, "bar"=>2}}

DisallowedType is raised if the XML contains attributes with type="yaml" or type="symbol". Use Hash.from_trusted_xml to parse this XML.

Custom disallowed_types can also be passed in the form of an array.

xml = <<-XML
  <?xml version="1.0" encoding="UTF-8"?>
    <hash>
      <foo type="integer">1</foo>
      <bar type="string">"David"</bar>
    </hash>
XML

hash = Hash.from_xml(xml, ['integer'])
# => ActiveSupport::XMLConverter::DisallowedType: Disallowed type attribute: "integer"

Note that passing custom disallowed types will override the default types, which are Symbol and YAML.

# File activesupport/lib/active_support/core_ext/hash/keys.rb, line 48
def assert_valid_keys(*valid_keys)
  valid_keys.flatten!
  each_key do |k|
    unless valid_keys.include?(k)
      raise ArgumentError.new("Unknown key: #{k.inspect}. Valid keys are: #{valid_keys.map(&:inspect).join(', ')}")
    end
  end
end

Validates all keys in a hash match *valid_keys, raising ArgumentError on a mismatch.

Note that keys are treated differently than HashWithIndifferentAccess, meaning that string and symbol keys will not match.

{ name: 'Rob', years: '28' }.assert_valid_keys(:name, :age) # => raises "ArgumentError: Unknown key: :years. Valid keys are: :name, :age"
{ name: 'Rob', age: '28' }.assert_valid_keys('name', 'age') # => raises "ArgumentError: Unknown key: :name. Valid keys are: 'name', 'age'"
{ name: 'Rob', age: '28' }.assert_valid_keys(:name, :age)   # => passes, raises nothing

# File activesupport/lib/active_support/core_ext/object/deep_dup.rb, line 43
def deep_dup
  hash = dup
  each_pair do |key, value|
    if key.frozen? && ::String === key
      hash[key] = value.deep_dup
    else
      hash.delete(key)
      hash[key.deep_dup] = value.deep_dup
    end
  end
  hash
end

Returns a deep copy of hash.

hash = { a: { b: 'b' } }
dup  = hash.deep_dup
dup[:a][:c] = 'c'

hash[:a][:c] # => nil
dup[:a][:c]  # => "c"

# File activesupport/lib/active_support/core_ext/hash/deep_merge.rb, line 18
def deep_merge(other_hash, &block)
  dup.deep_merge!(other_hash, &block)
end

Returns a new hash with self and other_hash merged recursively.

h1 = { a: true, b: { c: [1, 2, 3] } }
h2 = { a: false, b: { x: [3, 4, 5] } }

h1.deep_merge(h2) # => { a: false, b: { c: [1, 2, 3], x: [3, 4, 5] } }

Like with Hash#merge in the standard library, a block can be provided to merge values:

h1 = { a: 100, b: 200, c: { c1: 100 } }
h2 = { b: 250, c: { c1: 200 } }
h1.deep_merge(h2) { |key, this_val, other_val| this_val + other_val }
# => { a: 100, b: 450, c: { c1: 300 } }

# File activesupport/lib/active_support/core_ext/hash/deep_merge.rb, line 23
def deep_merge!(other_hash, &block)
  merge!(other_hash) do |key, this_val, other_val|
    if this_val.is_a?(Hash) && other_val.is_a?(Hash)
      this_val.deep_merge(other_val, &block)
    elsif block_given?
      block.call(key, this_val, other_val)
    else
      other_val
    end
  end
end

Same as deep_merge, but modifies self.

# File activesupport/lib/active_support/core_ext/hash/keys.rb, line 84
def deep_stringify_keys
  deep_transform_keys(&:to_s)
end

Returns a new hash with all keys converted to strings. This includes the keys from the root hash and from all nested hashes and arrays.

hash = { person: { name: 'Rob', age: '28' } }

hash.deep_stringify_keys
# => {"person"=>{"name"=>"Rob", "age"=>"28"}}

# File activesupport/lib/active_support/core_ext/hash/keys.rb, line 91
def deep_stringify_keys!
  deep_transform_keys!(&:to_s)
end

Destructively converts all keys to strings. This includes the keys from the root hash and from all nested hashes and arrays.

# File activesupport/lib/active_support/core_ext/hash/keys.rb, line 103
def deep_symbolize_keys
  deep_transform_keys { |key| key.to_sym rescue key }
end

Returns a new hash with all keys converted to symbols, as long as they respond to to_sym. This includes the keys from the root hash and from all nested hashes and arrays.

hash = { 'person' => { 'name' => 'Rob', 'age' => '28' } }

hash.deep_symbolize_keys
# => {:person=>{:name=>"Rob", :age=>"28"}}

# File activesupport/lib/active_support/core_ext/hash/keys.rb, line 110
def deep_symbolize_keys!
  deep_transform_keys! { |key| key.to_sym rescue key }
end

Destructively converts all keys to symbols, as long as they respond to to_sym. This includes the keys from the root hash and from all nested hashes and arrays.

# File activesupport/lib/active_support/core_ext/hash/keys.rb, line 65
def deep_transform_keys(&block)
  _deep_transform_keys_in_object(self, &block)
end

Returns a new hash with all keys converted by the block operation. This includes the keys from the root hash and from all nested hashes and arrays.

hash = { person: { name: 'Rob', age: '28' } }

hash.deep_transform_keys{ |key| key.to_s.upcase }
# => {"PERSON"=>{"NAME"=>"Rob", "AGE"=>"28"}}

# File activesupport/lib/active_support/core_ext/hash/keys.rb, line 72
def deep_transform_keys!(&block)
  _deep_transform_keys_in_object!(self, &block)
end

Destructively converts all keys by using the block operation. This includes the keys from the root hash and from all nested hashes and arrays.

# File activesupport/lib/active_support/core_ext/hash/deep_transform_values.rb, line 12
def deep_transform_values(&block)
  _deep_transform_values_in_object(self, &block)
end

Returns a new hash with all values converted by the block operation. This includes the values from the root hash and from all nested hashes and arrays.

hash = { person: { name: 'Rob', age: '28' } }

hash.deep_transform_values{ |value| value.to_s.upcase }
# => {person: {name: "ROB", age: "28"}}

# File activesupport/lib/active_support/core_ext/hash/deep_transform_values.rb, line 19
def deep_transform_values!(&block)
  _deep_transform_values_in_object!(self, &block)
end

Destructively converts all values by using the block operation. This includes the values from the root hash and from all nested hashes and arrays.

# File activesupport/lib/active_support/core_ext/hash/except.rb, line 12
def except(*keys)
  slice(*self.keys - keys)
end

Returns a hash that includes everything except given keys.

hash = { a: true, b: false, c: nil }
hash.except(:c)     # => { a: true, b: false }
hash.except(:a, :b) # => { c: nil }
hash                # => { a: true, b: false, c: nil }

This is useful for limiting a set of parameters to everything but a few known toggles:

@person.update(params[:person].except(:admin))

# File activesupport/lib/active_support/core_ext/hash/except.rb, line 20
def except!(*keys)
  keys.each { |key| delete(key) }
  self
end

Removes the given keys from hash and returns it.

hash = { a: true, b: false, c: nil }
hash.except!(:c) # => { a: true, b: false }
hash             # => { a: true, b: false }

# File activesupport/lib/active_support/core_ext/hash/slice.rb, line 23
def extract!(*keys)
  keys.each_with_object(self.class.new) { |key, result| result[key] = delete(key) if has_key?(key) }
end

Removes and returns the key/value pairs matching the given keys.

{ a: 1, b: 2, c: 3, d: 4 }.extract!(:a, :b) # => {:a=>1, :b=>2}
{ a: 1, b: 2 }.extract!(:a, :x)             # => {:a=>1}

# File activesupport/lib/active_support/core_ext/array/extract_options.rb, line 9
def extractable_options?
  instance_of?(Hash)
end

By default, only instances of Hash itself are extractable. Subclasses of Hash may implement this method and return true to declare themselves as extractable. If a Hash is extractable, Array#extract_options! pops it from the Array when it is the last element of the Array.

# File activesupport/lib/active_support/core_ext/hash/reverse_merge.rb, line 14
def reverse_merge(other_hash)
  other_hash.merge(self)
end

Merges the caller into other_hash. For example,

options = options.reverse_merge(size: 25, velocity: 10)

is equivalent to

options = { size: 25, velocity: 10 }.merge(options)

This is particularly useful for initializing an options hash with default values.

# File activesupport/lib/active_support/core_ext/hash/reverse_merge.rb, line 20
def reverse_merge!(other_hash)
  replace(reverse_merge(other_hash))
end

Destructive reverse_merge.

# File activesupport/lib/active_support/core_ext/hash/slice.rb, line 10
def slice!(*keys)
  omit = slice(*self.keys - keys)
  hash = slice(*keys)
  hash.default      = default
  hash.default_proc = default_proc if default_proc
  replace(hash)
  omit
end

Replaces the hash with only the given keys. Returns a hash containing the removed key/value pairs.

hash = { a: 1, b: 2, c: 3, d: 4 }
hash.slice!(:a, :b)  # => {:c=>3, :d=>4}
hash                 # => {:a=>1, :b=>2}

# File activesupport/lib/active_support/core_ext/hash/keys.rb, line 10
def stringify_keys
  transform_keys(&:to_s)
end

Returns a new hash with all keys converted to strings.

hash = { name: 'Rob', age: '28' }

hash.stringify_keys
# => {"name"=>"Rob", "age"=>"28"}

# File activesupport/lib/active_support/core_ext/hash/keys.rb, line 16
def stringify_keys!
  transform_keys!(&:to_s)
end

Destructively converts all keys to strings. Same as stringify_keys, but modifies self.

# File activesupport/lib/active_support/core_ext/hash/keys.rb, line 27
def symbolize_keys
  transform_keys { |key| key.to_sym rescue key }
end

Returns a new hash with all keys converted to symbols, as long as they respond to to_sym.

hash = { 'name' => 'Rob', 'age' => '28' }

hash.symbolize_keys
# => {:name=>"Rob", :age=>"28"}

# File activesupport/lib/active_support/core_ext/hash/keys.rb, line 34
def symbolize_keys!
  transform_keys! { |key| key.to_sym rescue key }
end

Destructively converts all keys to symbols, as long as they respond to to_sym. Same as symbolize_keys, but modifies self.

# File activesupport/lib/active_support/core_ext/object/to_query.rb, line 77
def to_query(namespace = nil)
  query = collect do |key, value|
    unless (value.is_a?(Hash) || value.is_a?(Array)) && value.empty?
      value.to_query(namespace ? "#{namespace}[#{key}]" : key)
    end
  end.compact

  query.sort! unless namespace.to_s.include?("[]")
  query.join("&")
end

Returns a string representation of the receiver suitable for use as a URL query string:

{name: 'David', nationality: 'Danish'}.to_query
# => "name=David&nationality=Danish"

An optional namespace can be passed to enclose key names:

{name: 'David', nationality: 'Danish'}.to_query('user')
# => "user%5Bname%5D=David&user%5Bnationality%5D=Danish"

The string pairs “key=value” that conform the query string are sorted lexicographically in ascending order.

This method is also aliased as to_param.

# File activesupport/lib/active_support/core_ext/hash/conversions.rb, line 75
def to_xml(options = {})
  require "active_support/builder" unless defined?(Builder)

  options = options.dup
  options[:indent]  ||= 2
  options[:root]    ||= "hash"
  options[:builder] ||= Builder::XmlMarkup.new(indent: options[:indent])

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

  root = ActiveSupport::XmlMini.rename_key(options[:root].to_s, options)

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

Returns a string containing an XML representation of its receiver:

{ foo: 1, bar: 2 }.to_xml
# =>
# <?xml version="1.0" encoding="UTF-8"?>
# <hash>
#   <foo type="integer">1</foo>
#   <bar type="integer">2</bar>
# </hash>

To do so, the method loops over the pairs and builds nodes that depend on the values. Given a pair key, value:

• If value is a hash there's a recursive call with key as :root.

• If value is an array there's a recursive call with key as :root, and key singularized as :children.

• If value is a callable object it must expect one or two arguments. Depending on the arity, the callable is invoked with the options hash as first argument with key as :root, and key singularized as second argument. The callable can add nodes by using options[:builder].

  {foo: lambda { |options, key| options[:builder].b(key) }}.to_xml
  # => "<b>foo</b>"
  

• If value responds to to_xml the method is invoked with key as :root.

  class Foo
    def to_xml(options)
      options[:builder].bar 'fooing!'
    end
  end
  
  { foo: Foo.new }.to_xml(skip_instruct: true)
  # =>
  # <hash>
  #   <bar>fooing!</bar>
  # </hash>
  

• Otherwise, a node with key as tag is created with a string representation of value as text node. If value is nil an attribute “nil” set to “true” is added. Unless the option :skip_types exists and is true, an attribute “type” is added as well according to the following mapping:

  XML_TYPE_NAMES = {
    "Symbol"     => "symbol",
    "Integer"    => "integer",
    "BigDecimal" => "decimal",
    "Float"      => "float",
    "TrueClass"  => "boolean",
    "FalseClass" => "boolean",
    "Date"       => "date",
    "DateTime"   => "dateTime",
    "Time"       => "dateTime"
  }
  

By default the root node is “hash”, but that's configurable via the :root option.

The default XML builder is a fresh instance of Builder::XmlMarkup. You can configure your own builder with the :builder option. The method also accepts options like :dasherize and friends, they are forwarded to the builder.

# File activesupport/lib/active_support/core_ext/hash/indifferent_access.rb, line 9
def with_indifferent_access
  ActiveSupport::HashWithIndifferentAccess.new(self)
end

Returns an ActiveSupport::HashWithIndifferentAccess out of its receiver:

{ a: 1 }.with_indifferent_access['a'] # => 1