What is the best way to chop a string into chunks

Question

I have been looking for an elegant and efficient way to chunk a string into substrings of a given length in Ruby.

So far, the best I could come up with is this:

def chunk(string, size)
  (0..(string.length-1)/size).map{|i|string[i*size,size]}
end

>> chunk("abcdef",3)
=> ["abc", "def"]
>> chunk("abcde",3)
=> ["abc", "de"]
>> chunk("abc",3)
=> ["abc"]
>> chunk("ab",3)
=> ["ab"]
>> chunk("",3)
=> []

You might want chunk("", n) to return [""] instead of []. If so, just add this as the first line of the method:

return [""] if string.empty?

Would you recommend any better solution?

Edit

Thanks to Jeremy Ruten for this elegant and efficient solution: [edit: NOT efficient!]

def chunk(string, size)
    string.scan(/.{1,#{size}}/)
end

Edit

The string.scan solution takes about 60 seconds to chop 512k into 1k chunks 10000 times, compared with the original slice-based solution which only takes 2.4 seconds.

Answer 1

Are there some other constraints you have in mind? Otherwise I'd be awfully tempted to do something simple like

[0..10].each {
   str[(i*w),w]
}