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

Use String#scan:

>> 'abcdefghijklmnopqrstuvwxyz'.scan(/.{4}/) => ['abcd', 'efgh', 'ijkl', 'mnop', 'qrst', 'uvwx'] >> 'abcdefghijklmnopqrstuvwxyz'.scan(/.{1,4}/) => ['abcd', 'efgh', 'ijkl', 'mnop', 'qrst', 'uvwx', 'yz'] >> 'abcdefghijklmnopqrstuvwxyz'.scan(/.{1,3}/) => ['abc', 'def', 'ghi', 'jkl', 'mno', 'pqr', 'stu', 'vwx', 'yz']