What is the %w “thing” in ruby?
%w means white space divided array
It is a literal, where it is a % then a r(regular expression), w(array), q(string) etc to denote different literals.
$ %w{1 2 3}
=> ["1", "2", "3"]
$ %w[1 2 3]
=> ["1", "2", "3"]
$ %w!a s d f!
=> ["a", "s", "d", "f"]
$ %w@a s d f@
=> ["a", "s", "d", "f"]
So you can see that you can use any character as long as it marks both the beginning and end of the content.
Here are some other examples:
Strings:
(%q or %Q)
$ %Q[ruby is cool]
=> "ruby is cool"
$ %q[ruby is "cool"]
=> "ruby is \"cool\""
Regex: (%r)
$ %r[(\w+)]
=> /(\w+)/
Sys command: (%x)
$ %x[date]
=> "Tue Mar 29 12:55:30 EDT 2011\n"
They cannot be nested because the %w means white space divided array. So if you try to do multi-level, it would look like this:
$ %w{1 %w{2 3 4} 5}
=> ["1", "%w{2", "3", "4}", "5"]
To accomplish this, you would need to use the more verbose syntax:
$ [1, [2,3,4], 5]
=> [1, [2, 3, 4], 5]
There are various forms of literal syntax you can use, with pretty much any paired delimiter, see http://www.ruby-doc.org/docs/ProgrammingRuby/html/language.html:
%w[one two three] # == ["one", "two", "three"]
%[one two three] # == "one two three"
%[one "two" three] # == "one \"two\" three"
%r[one two three] # == /one two three/
