Method name format

Question

What strings can be a method name for Ruby? I particularly want to know in what way a non word character can be part of a method name. Please give an exhaustive set of rules/lists.

Edit Phrogz' answers to the question that Josh Lee links has a link to the following page, but that is from several years ago, and is outdated. For example, Proc#() is missing. Does anyone know of an updated one?

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http://stackoverflow.com/questions/4378670/what-is-a-ruby-regex-to-match-a-function-name — Josh Lee, Oct 24 '12 at 15:17
@Josh Lee I looked at one of the answers there, but it seems outdated. — sawa, Oct 24 '12 at 15:24

score 3 · Answer 1 · answered Oct 24 '12 at 14:17

3

According to pickaxe (Programming Ruby, The Pragmatic Programmers):

Local variables, method parameters, and method names should all start with a lowercase letter or an underscore... Following this initial character, a name can be any combination of letters, digits, and underscores (with the proviso that the character following an @ sign may not be a digit)... Method names may end with the characters ?, !, and =.

answered Oct 24 '12 at 14:17

Chowlett

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`Array#[]` does not fit into this description. Nor does `Proc#()`. – sawa Oct 24 '12 at 15:12
Valid point, well made. I did think as I quoted that I was maybe missing something. – Chowlett Oct 24 '12 at 15:14
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Although I note that, while `def []` is fine, the parser has distinct difficulty with `def ()` – Chowlett Oct 24 '12 at 15:18
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`foo.(bar)` is syntax sugar for `foo.call(bar)` – Scott Olson Oct 24 '12 at 17:30

score 3 · Answer 2 · answered Oct 24 '12 at 22:55

3

Any sequence of Unicode characters is a valid method name. For example:

class Test
  define_method :'    ???    _    µµµµ . . . ' do puts 'Hello' end
end

Test.instance_methods
# => [:'    ???    _    µµµµ . . . ']

Test.new.send :'    ???    _    µµµµ . . . '
# Hello

answered Oct 24 '12 at 22:55

Jörg W Mittag

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I didn't know it what that flexible. This is a very informative answer. But I have a further question. Not all of them seem to be callable without using `send`. Which of them are callable without using `send`? – sawa Oct 24 '12 at 23:28

score 1 · Answer 3 · edited Jun 20 '20 at 09:12

You can use ASCII, UTF-8 and Unicode characters as the names of methods. I imagine that whitespace (\s) characters wouldn't work simply because the parser would complain. Just set up the magic line so Ruby knows what to expect.

http://www.oreillynet.com/ruby/blog/2007/10/fun_with_unicode_1.html and http://rosettacode.org/wiki/Unicode_variable_names#Ruby and http://www.sw.it.aoyama.ac.jp/2009/pub/IUC33-ruby1.9/. Phrogz has a nice regex in https://stackoverflow.com/a/4379197/128421 which covers the ASCII characters.

Also, here on Stack Overflow, this has been discussed nicely in "How does Ruby 1.9 handle character cases in source code?". Because of the age of that question I'm not marking this as a duplicate, but it does deserve to be referenced.

The question that should be asked though, is, should non-ASCII characters be used in method names? Yes, they're cute, and they might be symbolic, but they can be a pain to type, especially for those who don't have the ability to type in the characters for one reason or another. Creating a method name or constant containing π or λ might be hard to type if they're in a gem.

Also note that $KCODE, mentioned on several of the linked paged, is now deprecated in Ruby 1.9.1+ so you'll need to use magic lines.

After reading Jörg W Mittag's answer, I understand what you meant. — sawa, Oct 24 '12 at 23:30

Method name format

3 Answers3