get multiple substrings from a string in Ruby

Question

I have

tmp_body_symbols="things <st>hello</st> and <st>blue</st> by <st>orange</st>"
str1_markerstring = "<st>"
str2_markerstring = "</st>"
frags << tmp_body_symbols[/#{str1_markerstring}(.*?)#{str2_markerstring}/m, 1]

frags is "hello" but I want ["hello","blue","orange"]

How woudl I do that?

Answer 1

Use scan :

tmp_body_symbols.scan(/#{str1_markerstring}(.*?)#{str2_markerstring}/m).flatten

See also: Ruby docs for String#scan .

Answer 2

You can use Nokogiri to parse HTML/XML

require 'open-uri'
require 'nokogiri' 

doc = Nokogiri::HTML::Document.parse("things <st>hello</st> and <st>blue</st> by <st>orange</st>")
doc.css('st').map(&:text)
#=> ["hello", "blue", "orange"]

More Info : http://www.nokogiri.org/tutorials/parsing_an_html_xml_document.html

Answer 3

You can do this with a capture group, as @Doorknob has done, or without a capture group, by using a ("zero-width") positive look-behind and positive-lookahead:

tmp = "things <st>hello</st> and <st>blue</st> by <st>orange</st>"
s1 = "<st>"
s2 = "</st>"

tmp.scan(/(?<=#{ s1 }).*?(?=#{ s2 })/).flatten
  #=> ["hello", "blue", "orange"]

• (?<=#{ s1 }) , which evaluates to (?<=<st>) , is the positive look-behind.
• (?=#{ s2 }) , which evaluates to (?=</st>) , is the positive look-behind.
• ? following .* makes it "non-greedy". Without it:

tmp.scan(/(?<=#{ s1 }).*(?=#{ s2 })/).flatten
  #=> ["hello</st> and <st>blue</st> by <st>orange"]