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ruby

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444
\s
(group)
(?:alt1|alt2)
end
/x
----
=== Comment Complex Regular Expressions [[comment-regexes]]
Use `x` modifier for complex regexps.
This makes them more readable and you can add some useful comments.
[source,ruby]
----
regexp = /
start # some text
\s # white space char
(group) # first group
(?:alt1|alt2) # some alternation
end
/x
----
=== Use `gsub` with a Block or a Hash for Complex Replacements [[gsub-blocks]]
For complex replacements `sub`/`gsub` can be used with a block or a hash.
[source,ruby]
----
words = 'foo bar'
words.sub(/f/, 'f' => 'F') # => 'Foo bar'
words.gsub(/\w+/) { |word| word.capitalize } # => 'Foo Bar'
----
== Percent Literals
=== `%q` shorthand [[percent-q-shorthand]]
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.
[source,ruby]
----
# 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>)
----
=== `%q` [[percent-q]]
Avoid `%()` or the equivalent `%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.
[source,ruby]
----
# 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>)
----
=== `%r` [[percent-r]]
Use `%r` only for regular expressions matching _at least_ one `/` character.
[source,ruby]
----
# bad
%r{\s+}
# good
%r{^/(.*)$}
%r{^/blog/2011/(.*)$}
----
=== `%x` [[percent-x]]
Avoid the use of `%x` unless you're going to execute a command with backquotes in it (which is rather unlikely).
[source,ruby]
----
# bad
date = %x(date)