What does the Ruby method 'to_sym' do?
to_sym converts a string to a symbol. For example, "a".to_sym becomes :a.
It's not specific to Rails; vanilla Ruby has it as well.
It looks like in some versions of Ruby, a symbol could be converted to and from a Fixnum as well. But irb from Ruby 1.9.2-p0, from ruby-lang.org, doesn't allow that unless you add your own to_sym method to Fixnum. I'm not sure whether Rails does that, but it doesn't seem very useful in any case.
Expanding with useful details on the accepted answer by @cHao:to_sym is used when the original string variable needs to be converted to a symbol.
In some cases, you can avoid to_sym, by creating the variable as symbol, not string in the first place. For example:
my_str1 = 'foo'my_str2 = 'bar baz'my_sym1 = my_str1.to_symmy_sym2 = my_str2.to_sym# Best:my_sym1 = :foomy_sym2 = :'bar baz'or
array_of_strings = %w[foo bar baz]array_of_symbols = array_of_strings.map(&:to_sym)# Better:array_of_symbols = %w[foo bar baz].map(&:to_sym)# Bestarray_of_symbols = %i[foo bar baz]SEE ALSO:
When to use symbols instead of strings in Ruby?
When not to use to_sym in Ruby?
Best way to convert strings to symbols in hash
uppercase %I - Interpolated Array of symbols, separated by whitespace