10 - Percent Literals

• Use %()(it's a shorthand for %Q) for single-line strings which require both interpolation and embedded double-quotes. For multi-line strings, prefer heredocs.

  # bad (no interpolation needed)
  %(<div class="text">Some text</div>)
  # should be '<div class="text">Some text</div>'
  
  # bad (no double-quotes)
  %(This is #{quality} style)
  # should be "This is #{quality} style"
  
  # bad (multiple lines)
  %(<div>\n<span class="big">#{exclamation}</span>\n</div>)
  # should be a heredoc.
  
  # good (requires interpolation, has quotes, single line)
  %(<tr><td class="name">#{name}</td>)
  

• Avoid %q unless you have a string with both ' and " in it. Regular string literals are more readable and should be preferred unless a lot of characters would have to be escaped in them.

  # bad
  name = %q(Bruce Wayne)
  time = %q(8 o'clock)
  question = %q("What did you say?")
  
  # good
  name = 'Bruce Wayne'
  time = "8 o'clock"
  question = '"What did you say?"'
  quote = %q(<p class='quote'>"What did you say?"</p>)
  

• Use %r only for regular expressions matching at least one '/' character.

  # bad
  %r{\s+}
  
  # good
  %r{^/(.*)$}
  %r{^/blog/2011/(.*)$}
  

• Avoid the use of %x unless you're going to invoke a command with backquotes in it(which is rather unlikely).

  # bad
  date = %x(date)
  
  # good
  date = `date`
  echo = %x(echo `date`)
  

• Avoid the use of %s. It seems that the community has decided :"some string" is the preferred way to create a symbol with spaces in it.

• Prefer () as delimiters for all % literals, except %r. Since parentheses often appear inside regular expressions in many scenarios a less common character like { might be a better choice for a delimiter, depending on the regexp's content.

  # bad
  %w[one two three]
  %q{"Test's king!", John said.}
  
  # good
  %w(one two three)
  %q("Test's king!", John said.)