How to (easily) split string in Ruby with length and also delimiter - ruby

Question

I need to split a string in Ruby which has the following format:
[{a:1,b:2,c:3,d:4},{a:5,b:6,c:7,d:8},{a:9,b:10,c:11,d:12},{a:13,b:14,c:15,d:16}]
ie. it is a generated javascript array. Unfortunately the list is long and I would like to split it up on the array element separator comma after reaching a specific length suitable for editing it with a code editor, but in a way to keep the integrity of the elements. For example, the line above with a split width of 15 would become:
[{a:1,b:2,c:3,d:4},
{a:5,b:6,c:7,d:8},
{a:9,b:10,c:11,d:12},
{a:13,b:14,c:15,d:16}]
and with a width of 32 the text would be:
[{a:1,b:2,c:3,d:4},{a:5,b:6,c:7,d:8},
{a:9,b:10,c:11,d:12},{a:13,b:14,c:15,d:16}]
Beside of the classical "brute force" approach (loop through, check separator between } and { while increasing length, split if length greater than and valid separator found) is there a more "Rubyish" solution to the problem?
Edit: Naive approach attached, definitely not Rubyiish as I don't have a very strong Ruby background:
def split(what, length)
result = []
clength = 0
flag = FALSE
what_copy = what.to_s
what_copy.to_s.each_char do |c|
clength += 1
if clength > length
flag = TRUE
end
if c == '}' and flag
result << what[0 .. clength]
what = what[clength+1 .. -1]
clength = 0
flag = FALSE
end
end
pp result
sres = result.join("\n")
sres
end

Answer 1

You could use a regex with :
a non-greedy repetition of at least width-2 characters
followed by a }
followed by a , or a ].
data = "[{a:1,b:2,c:3,d:4},{a:5,b:6,c:7,d:8},{a:9,b:10,c:11,d:12},{a:13,b:14,c:15,d:16}]"
def split_data_with_min_width(text, width)
pattern = /
( # capturing group for split
.{#{width-2},}? # at least width-2 characters, but not more than needed
\} # closing curly brace
[,\]] # a comma or a closing bracket
)
/x # free spacing mode
text.split(pattern).reject(&:empty?).join("\n")
end
puts split_data_with_min_width(data, 15)
# [{a:1,b:2,c:3,d:4},
# {a:5,b:6,c:7,d:8},
# {a:9,b:10,c:11,d:12},
# {a:13,b:14,c:15,d:16},
# {a:17,b:18,c:19,d:20}]
puts split_data_with_min_width(data, 32)
# [{a:1,b:2,c:3,d:4},{a:5,b:6,c:7,d:8},
# {a:9,b:10,c:11,d:12},{a:13,b:14,c:15,d:16},
# {a:17,b:18,c:19,d:20}]
The method uses split with a capturing group instead of scan because the last part of the string might not be long enough:
"abcde".scan(/../)
# ["ab", "cd"]
"abcde".split(/(..)/).reject(&:empty?)
# ["ab", "cd", "e"]

Answer 2

Code
def doit(str, min_size)
r = /
(?: # begin non-capture group
.{#{min_size},}? # match at least min_size characters, non-greedily
(?=\{) # match '{' in a positive lookahead
| # or
.+\z # match one or more characters followed by end of string
) # close non-capture group
/x # free-spacing regex definition mode
str.scan(r)
end
Examples
str = "[{a:1,b:2,c:3,d:4},{a:5,b:6,c:7,d:8},{a:9,b:10,c:11,d:12},{a:13,b:14,c:15,d:16}]"
doit(str, 18) # same for all min_size <= 18
#=> ["[{a:1,b:2,c:3,d:4},",
# "{a:5,b:6,c:7,d:8},",
# "{a:9,b:10,c:11,d:12},",
# "{a:13,b:14,c:15,d:16}]"]
doit(str, 19)
#=> ["[{a:1,b:2,c:3,d:4},",
# "{a:5,b:6,c:7,d:8},{a:9,b:10,c:11,d:12},",
# "{a:13,b:14,c:15,d:16}]"]
doit(str, 20)
#=> ["[{a:1,b:2,c:3,d:4},{a:5,b:6,c:7,d:8},",
# "{a:9,b:10,c:11,d:12},",
# "{a:13,b:14,c:15,d:16}]"]
doit(str, 21)
#=> ["[{a:1,b:2,c:3,d:4},{a:5,b:6,c:7,d:8},",
# "{a:9,b:10,c:11,d:12},",
# "{a:13,b:14,c:15,d:16}]"]
doit(str, 22) # same for 23 <= min_size <= 37
#=> ["[{a:1,b:2,c:3,d:4},{a:5,b:6,c:7,d:8},",
# "{a:9,b:10,c:11,d:12},{a:13,b:14,c:15,d:16}]"]
doit(str, 38) # same for 39 <= min_size <= 58
#=> ["[{a:1,b:2,c:3,d:4},{a:5,b:6,c:7,d:8},{a:9,b:10,c:11,d:12},",
# "{a:13,b:14,c:15,d:16}]"]
doit(str, 59) # same for min_size > 59
#=> ["[{a:1,b:2,c:3,d:4},{a:5,b:6,c:7,d:8},{a:9,b:10,c:11,d:12},{a:13,b:14,c:15,d:16}]"]

Answer 3

Like this?
2.3.1 :007 > a
=> "[{a:1,b:2,c:3,d:4},{a:5,b:6,c:7,d:8},{a:9,b:10,c:11,d:12},{a:13,b:14,c:15,d:16}]"
2.3.1 :008 > q = a.gsub("},", "},\n")
=> "[{a:1,b:2,c:3,d:4},\n{a:5,b:6,c:7,d:8},\n{a:9,b:10,c:11,d:12},\n{a:13,b:14,c:15,d:16}]"
2.3.1 :009 > puts q
[{a:1,b:2,c:3,d:4},
{a:5,b:6,c:7,d:8},
{a:9,b:10,c:11,d:12},
{a:13,b:14,c:15,d:16}]
=> nil
2.3.1 :010 >