There's a few useful shorthand ways to create certain objects in Ruby, a couple of obvious ones are [] to create an Array and {} to create a Hash (Or block/Proc). There's some not so obvious ones too, for creating strings, regexes and executing shell commands.
With all of the examples I've used {} as the delimiter characters, but you can use a variety of characters. Personally I tend to use {} unless the string contains them, in which case I'll use // or @@. My only exception appears to be %w, for which I tend to use ().
Strings
% and %Q are the same as using double quotes, including string interpolation. Really useful when you want to create a string that contains double quotes, but without the hassle of escaping them.
%{} # => ""
%Q{} # => ""
%{caius} # => "caius"
%{caius #{5}} # => "caius 5"
%{some "foo" thing} # => "some \"foo\" thing"
%q is equivalent to using single quotes. Behaves exactly the same, no string interpolation.
%q{} # => ''
%q{caius} # => "caius"
%q{caius #{5}} # => "caius \#{5}"
Arrays
%w is the equivalent of using String#split. It takes a string and splits it on whitespace. With the added bonus of being able to escape whitespace too. %W allows string interpolation.
%w(foo bar sed) # => ["foo", "bar", "sed"]
%w(foo\ bar sed) # => ["foo bar", "sed"]
%W(foo #{5} bar) # => ["foo", "5", "bar"]
Regexes
%r is just like using // to create a regexp object. Comes in handy when you're writing a regex containing / as you don't have to continually escape it.
%r{foo|bar} # => /foo|bar/
%r{foo/bar} # => /foo\/bar/
Symbols
%s creates a symbol, just like writing :foo manually. It takes care of escaping the symbol, but unlike :"" it doesn't allow string interpolation however.
%s{foo} # => :foo
%s{foo/bar} # => :"foo/bar"
:"foo-#{5}" # => :"foo-5"
%s{foo-#{5}} # => :"foo-\#{5}"
Shelling out
%x is the same as backticks (``), executes the command in a shell and returns the output as a string. And just like backticks it supports string interpolation.
`echo hi` # => "hi\n"
%x{echo hi} # => "hi\n"
%x{echo #{5}} # => "5\n"
Oddly, what I learned from this wasn't new shortcuts as I believe I had seen them all before, but the fact that you can use different delimiters! This detail had escaped me.
Don't forget the sprintf shortcut--these are equivalent:
sprintf("%5.1f", 345.6789) # "345.7" "%5.1f" % 345.6789 # "345.7"as are these:
sprintf("%6.2f, %05d", 345.6789, 123) # "345.68, 00123" "%6.2f, %05d" % [345.6789, 123] # "345.68, 00123"@ed: That isn't strictly a shortcut in the way the others are, it's a method on String. String#% to be precise :)
True, but it is kinda cool and not very well-known, don'cha think? :)
Timely find for me, I've working on a website where there are a lot of pre-existing articles to post and have been furiously escaping either " or ' . What a pain! I didn't know about using the %Q{} to avoid the mess. THANKS!
@Ed: I guess it isn't that well known, I've just read the String documentation a fair bit and know most of the methods in there ;) Still great to point it out to people though!
@FlyboyArt: I'm glad I could help! My "justification" for blogging is if it helps just one person, it was worth sharing. :)
I've found that carets (^) work quite well as delimiters. I rarely use them in text.
I was curious so other people might be too: %W doesn't split interpolated strings.
Hi Caius, this is a very interesting post.
So interesting that I think it's worth to reproduce your thoughts as a screencast. Check out RubyPulse Episodes 0.33 + 0.34 ... so... actually your post is woth TWO screencasts ;-) GREAT!
~ aaalex
Thanks a lot Caius.
I've learned a lot in your post. Moreover, it helped me fixing some parts inside my highlighter (see ie http://prism-pastebin.heroku.com/28)