Rails comes with the word_wrap helper which can split long lines based on a given line width. It always splits at whitespace so long words won't get split / cut.

In rails/console:

lines = helper.word_wrap("a b c d e text longword", line_width: 5)
#=> "a b c\nd e\ntext\nlongword"

puts lines

Output:

a b c
d e
text
longword

Note that it returns a string, not an array.

That can be done in pure-Ruby as follows¹.

def text_splitter(text, line_size)
  text.gsub(/(?:.{1,#{line_size}}|\S+)\K(?:$|\s)/, "\n")
end

text = "Beware the Jabberwock, my son! The jaws that bite, the claws that catch!"

puts text_splitter(text, 30)
0        1         2         3
123456789012345678901234567890
Beware the Jabberwock, my son!
The jaws that bite, the claws
that catch!

puts text_splitter(text, 20)
0        1         2
12345678901234567890
Beware the
Jabberwock, my son!
The jaws that bite,
the claws that
catch!

puts text_splitter(text, 10)
0        1
1234567890
Beware the
Jabberwock,
my son!
The jaws
that bite,
the claws
that
catch!

puts text_splitter(text, 8)
0
12345678
Beware
the
Jabberwock,
my son!
The jaws
that
bite,
the
claws
that
catch!

The regular expression can be broken down as follows (for line_size = 10):

(?:         # begin non-capture group
  .{1,10}   # match 1-10 chars
  |         # or 
  \S+       # match >= 1 non-whitespace chars
)           # end non-capture group
\K          # reset start of match and discard all chars previously matched
(?:$|\s)    # match the end of the string or a whitespace chars

^{1. Sample text is from Lewis Carrol's peom, "Jabberwocky".}