Symbol

A Symbol is a name: :width, :m3, :round. Two Symbols of the same name are the same value, so they compare quickly and make good keys. Symbols name parameters (param(:width, ...)), key Maps ({ width: 10 } is keyed by :width) and choose options (stroke(1, cap: :round)).

A Symbol is written :name, or quoted for a name that isn’t an identifier: :"a b". A double-quoted Symbol decodes its escapes and interpolates (:"part_#{i}"), a single-quoted one doesn’t. %i[m3 m4] is the Array [:m3, :m4]. See Syntax.

As in Ruby, a Symbol reads as its name (puts, interpolation and join give m3) and inspects with its colon (:m3). One that :name couldn’t read back inspects quoted. A Symbol is never equal to a String: :m3 == "m3" is false.

size = :m3
puts size                  # m3
puts "thread #{size}"      # thread m3
puts size.inspect          # :m3
puts :"a b".inspect        # :"a b"
i = 2
puts :"part_#{i}".inspect  # :part_2
puts size == :m3           # true

to_s

sym.to_s

The Symbol’s name. Returns: String.

to_sym

sym.to_sym

The Symbol itself (a String’s to_sym makes one). Returns: Symbol.

puts :m3.to_s.inspect      # "m3"
puts "m4".to_sym.inspect   # :m4