Methods
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Class Public methods
from_trusted_xml(xml)

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
134 def from_trusted_xml(xml)
135   from_xml xml, []
136 end
from_xml(xml, disallowed_types = nil)

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/conversions.rb
129 def from_xml(xml, disallowed_types = nil)
130   ActiveSupport::XMLConverter.new(xml, disallowed_types).to_h
131 end
Instance Public methods
assert_valid_keys(*valid_keys)

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/hash/keys.rb
48 def assert_valid_keys(*valid_keys)
49   valid_keys.flatten!
50   each_key do |k|
51     unless valid_keys.include?(k)
52       raise ArgumentError.new("Unknown key: #{k.inspect}. Valid keys are: #{valid_keys.map(&:inspect).join(', ')}")
53     end
54   end
55 end
deep_dup()

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/object/deep_dup.rb
43 def deep_dup
44   hash = dup
45   each_pair do |key, value|
46     if key.frozen? && ::String === key
47       hash[key] = value.deep_dup
48     else
49       hash.delete(key)
50       hash[key.deep_dup] = value.deep_dup
51     end
52   end
53   hash
54 end
deep_merge(other_hash, &block)

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
18 def deep_merge(other_hash, &block)
19   dup.deep_merge!(other_hash, &block)
20 end
deep_merge!(other_hash, &block)

Same as deep_merge, but modifies self.

   # File activesupport/lib/active_support/core_ext/hash/deep_merge.rb
23 def deep_merge!(other_hash, &block)
24   merge!(other_hash) do |key, this_val, other_val|
25     if this_val.is_a?(Hash) && other_val.is_a?(Hash)
26       this_val.deep_merge(other_val, &block)
27     elsif block_given?
28       block.call(key, this_val, other_val)
29     else
30       other_val
31     end
32   end
33 end
deep_stringify_keys()

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
84 def deep_stringify_keys
85   deep_transform_keys(&:to_s)
86 end
deep_stringify_keys!()

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
91 def deep_stringify_keys!
92   deep_transform_keys!(&:to_s)
93 end
deep_symbolize_keys()

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
103 def deep_symbolize_keys
104   deep_transform_keys { |key| key.to_sym rescue key }
105 end
deep_symbolize_keys!()

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
110 def deep_symbolize_keys!
111   deep_transform_keys! { |key| key.to_sym rescue key }
112 end
deep_transform_keys(&block)

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
65 def deep_transform_keys(&block)
66   _deep_transform_keys_in_object(self, &block)
67 end
deep_transform_keys!(&block)

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/keys.rb
72 def deep_transform_keys!(&block)
73   _deep_transform_keys_in_object!(self, &block)
74 end
deep_transform_values(&block)

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
12 def deep_transform_values(&block)
13   _deep_transform_values_in_object(self, &block)
14 end
deep_transform_values!(&block)

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/deep_transform_values.rb
19 def deep_transform_values!(&block)
20   _deep_transform_values_in_object!(self, &block)
21 end
except(*keys)

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
12 def except(*keys)
13   slice(*self.keys - keys)
14 end
except!(*keys)

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/except.rb
20 def except!(*keys)
21   keys.each { |key| delete(key) }
22   self
23 end
extract!(*keys)

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/hash/slice.rb
23 def extract!(*keys)
24   keys.each_with_object(self.class.new) { |key, result| result[key] = delete(key) if has_key?(key) }
25 end
extractable_options?()

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/array/extract_options.rb
 9 def extractable_options?
10   instance_of?(Hash)
11 end
nested_under_indifferent_access()

Called when object is nested under an object that receives with_indifferent_access. This method will be called on the current object by the enclosing object and is aliased to with_indifferent_access by default. Subclasses of Hash may overwrite this method to return self if converting to an ActiveSupport::HashWithIndifferentAccess would not be desirable.

b = { b: 1 }
{ a: b }.with_indifferent_access['a'] # calls b.nested_under_indifferent_access
# => {"b"=>1}
reverse_merge(other_hash)

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.

Also aliased as: with_defaults
   # File activesupport/lib/active_support/core_ext/hash/reverse_merge.rb
14 def reverse_merge(other_hash)
15   other_hash.merge(self)
16 end
reverse_merge!(other_hash)

Destructive reverse_merge.

Also aliased as: reverse_update, with_defaults!
   # File activesupport/lib/active_support/core_ext/hash/reverse_merge.rb
20 def reverse_merge!(other_hash)
21   replace(reverse_merge(other_hash))
22 end
reverse_update(other_hash)
Alias for: reverse_merge!
slice!(*keys)

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/slice.rb
10 def slice!(*keys)
11   omit = slice(*self.keys - keys)
12   hash = slice(*keys)
13   hash.default      = default
14   hash.default_proc = default_proc if default_proc
15   replace(hash)
16   omit
17 end
stringify_keys()

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
10 def stringify_keys
11   transform_keys(&:to_s)
12 end
stringify_keys!()

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

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

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"}
Also aliased as: to_options
   # File activesupport/lib/active_support/core_ext/hash/keys.rb
27 def symbolize_keys
28   transform_keys { |key| key.to_sym rescue key }
29 end
symbolize_keys!()

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

Also aliased as: to_options!
   # File activesupport/lib/active_support/core_ext/hash/keys.rb
34 def symbolize_keys!
35   transform_keys! { |key| key.to_sym rescue key }
36 end
to_options()
Alias for: symbolize_keys
to_options!()
Alias for: symbolize_keys!
to_param(namespace = nil)
Alias for: to_query
to_query(namespace = nil)

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.

Also aliased as: to_param
   # File activesupport/lib/active_support/core_ext/object/to_query.rb
77 def to_query(namespace = nil)
78   query = collect do |key, value|
79     unless (value.is_a?(Hash) || value.is_a?(Array)) && value.empty?
80       value.to_query(namespace ? "#{namespace}[#{key}]" : key)
81     end
82   end.compact
83 
84   query.sort! unless namespace.to_s.include?("[]")
85   query.join("&")
86 end
to_xml(options = {})

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/conversions.rb
75 def to_xml(options = {})
76   require "active_support/builder" unless defined?(Builder)
77 
78   options = options.dup
79   options[:indent]  ||= 2
80   options[:root]    ||= "hash"
81   options[:builder] ||= Builder::XmlMarkup.new(indent: options[:indent])
82 
83   builder = options[:builder]
84   builder.instruct! unless options.delete(:skip_instruct)
85 
86   root = ActiveSupport::XmlMini.rename_key(options[:root].to_s, options)
87 
88   builder.tag!(root) do
89     each { |key, value| ActiveSupport::XmlMini.to_tag(key, value, options) }
90     yield builder if block_given?
91   end
92 end
with_defaults(other_hash)
Alias for: reverse_merge
with_defaults!(other_hash)
Alias for: reverse_merge!
with_indifferent_access()

Returns an ActiveSupport::HashWithIndifferentAccess out of its receiver:

{ a: 1 }.with_indifferent_access['a'] # => 1
   # File activesupport/lib/active_support/core_ext/hash/indifferent_access.rb
 9 def with_indifferent_access
10   ActiveSupport::HashWithIndifferentAccess.new(self)
11 end