class Symbol

A Symbol object represents a named identifier inside the Ruby interpreter.

You can create a Symbol object explicitly with:

A symbol literal.

The same Symbol object will be created for a given name or string for the duration of a program’s execution, regardless of the context or meaning of that name. Thus if Fred is a constant in one context, a method in another, and a class in a third, the Symbol :Fred will be the same object in all three contexts.

module One
  class Fred
  end
  $f1 = :Fred
end
module Two
  Fred = 1
  $f2 = :Fred
end
def Fred()
end
$f3 = :Fred
$f1.object_id   #=> 2514190
$f2.object_id   #=> 2514190
$f3.object_id   #=> 2514190

Constant, method, and variable names are returned as symbols:

module One
  Two = 2
  def three; 3 end
  @four = 4
  @@five = 5
  $six = 6
end
seven = 7

One.constants
# => [:Two]
One.instance_methods(true)
# => [:three]
One.instance_variables
# => [:@four]
One.class_variables
# => [:@@five]
global_variables.grep(/six/)
# => [:$six]
local_variables
# => [:seven]

A Symbol object differs from a String object in that a Symbol object represents an identifier, while a String object represents text or data.

What’s Here

First, what’s elsewhere. Class Symbol:

Inherits from class Object.
Includes module Comparable.

Here, class Symbol provides methods that are useful for:

Methods for Querying

::all_symbols: Returns an array of the symbols currently in Ruby’s symbol table.
=~: Returns the index of the first substring in symbol that matches a given Regexp or other object; returns nil if no match is found.
[], slice : Returns a substring of symbol determined by a given index, start/length, or range, or string.
empty?: Returns true if self.length is zero; false otherwise.
encoding: Returns the Encoding object that represents the encoding of symbol.
end_with?: Returns true if symbol ends with any of the given strings.
match: Returns a MatchData object if symbol matches a given Regexp; nil otherwise.
match?: Returns true if symbol matches a given Regexp; false otherwise.
length, size: Returns the number of characters in symbol.
start_with?: Returns true if symbol starts with any of the given strings.

Methods for Comparing

<=>: Returns -1, 0, or 1 as a given symbol is smaller than, equal to, or larger than symbol.
==, ===: Returns true if a given symbol has the same content and encoding.
casecmp: Ignoring case, returns -1, 0, or 1 as a given symbol is smaller than, equal to, or larger than symbol.
casecmp?: Returns true if symbol is equal to a given symbol after Unicode case folding; false otherwise.

Methods for Converting

capitalize: Returns symbol with the first character upcased and all other characters downcased.
downcase: Returns symbol with all characters downcased.
inspect: Returns the string representation of self as a symbol literal.
name: Returns the frozen string corresponding to symbol.
succ, next: Returns the symbol that is the successor to symbol.
swapcase: Returns symbol with all upcase characters downcased and all downcase characters upcased.
to_proc: Returns a Proc object which responds to the method named by symbol.
to_s, id2name: Returns the string corresponding to self.
to_sym, intern: Returns self.
upcase: Returns symbol with all characters upcased.

Public Class Methods

all_symbols

() → Array[Symbol]

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.1.3/core/symbol.rbs, line 130
def self.all_symbols: () -> Array[Symbol]

Returns an array of all symbols currently in Ruby’s symbol table:

Symbol.all_symbols.size    # => 9334
Symbol.all_symbols.take(3) # => [:!, :"\"", :"#"]

json_create (o)

(Hash[String, String] object) → instance

Source

# File vendor/bundle/ruby/4.0.0/gems/json-2.21.2/lib/json/add/symbol.rb, line 49
def self.json_create(o)
  o['s'].to_sym
end

See as_json.

Public Instance Methods

<=>

(Symbol object) → (-1 | 0 | 1)
(untyped) → (-1 | 0 | 1)?

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.1.3/core/symbol.rbs, line 155
def <=>: (Symbol object) -> (-1 | 0 | 1)
         | (untyped) -> (-1 | 0 | 1)?

Compares self and other, using String#<=>.

Returns:

self.to_s <=> other.to_s, if other is a symbol.
nil, otherwise.

Examples:

:bar <=> :foo  # => -1
:foo <=> :foo  # => 0
:foo <=> :bar  # => 1
:foo <=> 'bar' # => nil

Class Symbol includes module Comparable, each of whose methods uses Symbol#<=> for comparison.

Related: String#<=>.

(untyped object) → bool

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.1.3/core/symbol.rbs, line 164
def ==: (untyped object) -> bool

Returns true if object is the same object as self, false otherwise.

Also aliased as: ===

===

(untyped object) → bool

Returns true if object is the same object as self, false otherwise.

Alias for: ==

(Regexp regex) → Integer?
[T] (String::_MatchAgainst[String, T] object) → T

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.1.3/core/symbol.rbs, line 178
def =~: (Regexp regex) -> Integer?
        | [T] (String::_MatchAgainst[String, T] object) -> T

Equivalent to symbol.to_s =~ object, including possible updates to global variables; see String#=~.

[]

(int start, ?int length) → String?
(range[int?] range) → String?
(Regexp regexp, ?MatchData::capture backref) → String?
(String substring) → String?

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.1.3/core/symbol.rbs, line 191
def []: (int start, ?int length) -> String?
        | (range[int?] range) -> String?
        | (Regexp regexp, ?MatchData::capture backref) -> String?
        | (String substring) -> String?

Equivalent to symbol.to_s[]; see String#[].

Also aliased as: slice

as_json (*)

(*untyped) → Hash[String, String]

Source

# File vendor/bundle/ruby/4.0.0/gems/json-2.21.2/lib/json/add/symbol.rb, line 23
def as_json(*)
  {
    JSON.create_id => self.class.name,
    's'            => to_s,
  }
end

Methods Symbol#as_json and Symbol.json_create may be used to serialize and deserialize a Symbol object; see Marshal.

Method Symbol#as_json serializes self, returning a 2-element hash representing self:

require 'json/add/symbol'
x = :foo.as_json
# => {"json_class"=>"Symbol", "s"=>"foo"}

Method JSON.create deserializes such a hash, returning a Symbol object:

Symbol.json_create(x) # => :foo

Methods Symbol#as_json and Symbol.json_create may be used to serialize and deserialize a Symbol object; see Marshal.

Method Symbol#as_json serializes self, returning a 2-element hash representing self:

require 'json/add/symbol'
x = :foo.as_json
# => {"json_class"=>"Symbol", "s"=>"foo"}

Method JSON.create deserializes such a hash, returning a Symbol object:

Symbol.json_create(x) # => :foo

capitalize

() → Symbol
(:ascii | :lithuanian | :turkic) → Symbol
(:lithuanian, :turkic) → Symbol
(:turkic, :lithuanian) → Symbol

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.1.3/core/symbol.rbs, line 204
def capitalize: () -> Symbol
                | (:ascii | :lithuanian | :turkic) -> Symbol
                | (:lithuanian, :turkic) -> Symbol
                | (:turkic, :lithuanian) -> Symbol

Equivalent to sym.to_s.capitalize.to_sym.

See String#capitalize.

casecmp

(untyped object) → (-1 | 0 | 1)?

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.1.3/core/symbol.rbs, line 241
def casecmp: (untyped object) -> (-1 | 0 | 1)?

Like Symbol#<=>, but case-insensitive; equivalent to self.to_s.casecmp(object.to_s):

lower = :abc
upper = :ABC
upper.casecmp(lower) # => 0
lower.casecmp(lower) # => 0
lower.casecmp(upper) # => 0

Returns nil if self and object have incompatible encodings, or if object is not a symbol:

sym = 'äöü'.encode("ISO-8859-1").to_sym
other_sym = 'ÄÖÜ'
sym.casecmp(other_sym) # => nil
:foo.casecmp(2)        # => nil

Unlike Symbol#casecmp?, case-insensitivity does not work for characters outside of ‘A’..‘Z’ and ‘a’..‘z’:

lower = :äöü
upper = :ÄÖÜ
upper.casecmp(lower) # => -1
lower.casecmp(lower) # => 0
lower.casecmp(upper) # => 1

casecmp?

(untyped object) → bool?

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.1.3/core/symbol.rbs, line 274
def casecmp?: (untyped object) -> bool?

Returns true if self and object are equal after Unicode case folding, otherwise false:

lower = :abc
upper = :ABC
upper.casecmp?(lower) # => true
lower.casecmp?(lower) # => true
lower.casecmp?(upper) # => true

Returns nil if self and object have incompatible encodings, or if object is not a symbol:

sym = 'äöü'.encode("ISO-8859-1").to_sym
other_sym = 'ÄÖÜ'
sym.casecmp?(other_sym) # => nil
:foo.casecmp?(2)        # => nil

Unlike Symbol#casecmp, works for characters outside of ‘A’..‘Z’ and ‘a’..‘z’:

lower = :äöü
upper = :ÄÖÜ
upper.casecmp?(lower) # => true
lower.casecmp?(lower) # => true
lower.casecmp?(upper) # => true

downcase

() → Symbol
(:ascii | :fold | :lithuanian | :turkic) → Symbol
(:lithuanian, :turkic) → Symbol
(:turkic, :lithuanian) → Symbol

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.1.3/core/symbol.rbs, line 286
def downcase: () -> Symbol
              | (:ascii | :fold | :lithuanian | :turkic) -> Symbol
              | (:lithuanian, :turkic) -> Symbol
              | (:turkic, :lithuanian) -> Symbol

Equivalent to sym.to_s.downcase.to_sym.

See String#downcase.

Related: Symbol#upcase.

empty?

() → bool

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.1.3/core/symbol.rbs, line 297
def empty?: () -> bool

Returns true if self is :'', false otherwise.

encoding

() → Encoding

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.1.3/core/symbol.rbs, line 305
def encoding: () -> Encoding

Equivalent to self.to_s.encoding; see String#encoding.

end_with?

(*string suffixes) → bool

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.1.3/core/symbol.rbs, line 313
def end_with?: (*string suffixes) -> bool

Equivalent to self.to_s.end_with?; see String#end_with?.

id2name

() → String

Alias for: to_s

inspect

() → String

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.1.3/core/symbol.rbs, line 332
def inspect: () -> String

Returns a string representation of self (including the leading colon):

:foo.inspect # => ":foo"

Related: Symbol#to_s, Symbol#name.

intern

() → self

Alias for: to_sym

length

() → Integer

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.1.3/core/symbol.rbs, line 347
def length: () -> Integer

Equivalent to self.to_s.length; see String#length.

Also aliased as: size

match

(Regexp | string pattern, ?int offset) → MatchData?
[T] (Regexp | string pattern, ?int offset) { (MatchData matchdata) → T } → T?

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.1.3/core/symbol.rbs, line 357
def match: (Regexp | string pattern, ?int offset) -> MatchData?
           | [T] (Regexp | string pattern, ?int offset) { (MatchData matchdata) -> T } -> T?

Equivalent to self.to_s.match, including possible updates to global variables; see String#match.

match?

(Regexp | string pattern, ?int offset) → bool

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.1.3/core/symbol.rbs, line 366
def match?: (Regexp | string pattern, ?int offset) -> bool

Equivalent to sym.to_s.match?; see String#match.

name

() → String

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.1.3/core/symbol.rbs, line 389
def name: () -> String

Returns a frozen string representation of self (not including the leading colon):

:foo.name         # => "foo"
:foo.name.frozen? # => true

() → Symbol

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.1.3/core/symbol.rbs, line 375
def next: () -> Symbol

Equivalent to self.to_s.succ.to_sym:

:foo.succ # => :fop

Related: String#succ.

Also aliased as: succ

size

() → Integer

Equivalent to self.to_s.length; see String#length.

Alias for: length

slice

(int start, ?int length) → String?
(range[int?] range) → String?
(Regexp regexp, ?MatchData::capture backref) → String?
(String substring) → String?

Equivalent to symbol.to_s[]; see String#[].

Alias for: []

start_with?

(*Regexp | string prefixes) → bool

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.1.3/core/symbol.rbs, line 407
def start_with?: (*Regexp | string prefixes) -> bool

Equivalent to self.to_s.start_with?; see String#start_with?.

succ

() → Symbol

Equivalent to self.to_s.succ.to_sym:

:foo.succ # => :fop

Related: String#succ.

Alias for: next

swapcase

() → Symbol
(:ascii | :lithuanian | :turkic) → Symbol
(:lithuanian, :turkic) → Symbol
(:turkic, :lithuanian) → Symbol

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.1.3/core/symbol.rbs, line 429
def swapcase: () -> Symbol
              | (:ascii | :lithuanian | :turkic) -> Symbol
              | (:lithuanian, :turkic) -> Symbol
              | (:turkic, :lithuanian) -> Symbol

Equivalent to sym.to_s.swapcase.to_sym.

See String#swapcase.

to_json (state = nil, *a)

(?JSON::State? state) → String

Source

# File vendor/bundle/ruby/4.0.0/gems/json-2.21.2/lib/json/add/symbol.rb, line 39
def to_json(state = nil, *a)
  state = ::JSON::State.from_state(state)
  if state.strict?
    super
  else
    as_json.to_json(state, *a)
  end
end

Returns a JSON string representing self:

require 'json/add/symbol'
puts :foo.to_json

Output:

# {"json_class":"Symbol","s":"foo"}

Returns a JSON string representing self:

require 'json/add/symbol'
puts :foo.to_json

Output:

# {"json_class":"Symbol","s":"foo"}

Calls superclass method Object#to_json

to_proc

() → Proc

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.1.3/core/symbol.rbs, line 446
def to_proc: () -> Proc

Returns a Proc object which calls the method with name of self on the first parameter and passes the remaining parameters to the method.

proc = :to_s.to_proc   # => #<Proc:0x000001afe0e48680(&:to_s) (lambda)>
proc.call(1000)        # => "1000"
proc.call(1000, 16)    # => "3e8"
(1..3).collect(&:to_s) # => ["1", "2", "3"]

to_s

() → String

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.1.3/core/symbol.rbs, line 458
def to_s: () -> String

Returns a string representation of self (not including the leading colon):

:foo.to_s # => "foo"

Also aliased as: id2name

to_sym

() → self

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.1.3/core/symbol.rbs, line 468
def to_sym: () -> self

Returns self.

Related: String#to_sym.

Also aliased as: intern

upcase

() → Symbol
(:ascii | :lithuanian | :turkic) → Symbol
(:lithuanian, :turkic) → Symbol
(:turkic, :lithuanian) → Symbol

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.1.3/core/symbol.rbs, line 478
def upcase: () -> Symbol
            | (:ascii | :lithuanian | :turkic) -> Symbol
            | (:lithuanian, :turkic) -> Symbol
            | (:turkic, :lithuanian) -> Symbol

Equivalent to sym.to_s.upcase.to_sym.

See String#upcase.