Using String#split Method

Question

By default, the #split method work as follows:

"id,name,title(first_name,last_name)".split(",")

will give you following output:

["id", "name", "title(first_name", "last_name)"]

But I want something like following:

["id", "name", "title(first_name,last_name)"]

So, I use following regex (from the this answer) using split to get desired output:

"id,name,title(first_name,last_name)".split(/,(?![^(]*\))/)

But, again when I use another string, which is my actual input above, the logic fails. My actual string is:

"id,name,title(first_name,last_name,address(street,pincode(id,code)))"

and it is giving following output:

["id", "name", "title(first_name", "last_name", "address(street", "pincode(id,code)))"]

rather than

["id", "name", "title(first_name,last_name,address(street,pincode(id,code)))"]

Answer 1

def doit(str)
  split_here = 0.chr
  stack = 0
  s = str.gsub(/./) do |c|
    ret = c
    case c
    when '('
      stack += 1
    when ','
      ret = split_here, if stack.zero?
    when ')'
      raise(RuntimeError, "parens are unbalanced") if stack.zero?
      stack -= 1
    end
    ret
  end
  raise(RuntimeError, "parens are unbalanced, stack at end=#{stack}") if stack > 0
  s.split(split_here)
end

doit "id,name,title(first_name,last_name)"
  #=> ["id", "name", "title(first_name,last_name)"]
doit "id,name,title(first_name,last_name,address(street,pincode(id,code)))"
  #=> ["id", "name", "title(first_name,last_name,address(street,pincode(id,code)))"]
doit "a,b(c(d),e,f)"
  #=> ["a", "b(c(d),e,f)"]
doit "id,name,title(first_name,last_name),pub(name,address)"
  #=> ["id", "name", "title(first_name,last_name)", "pub(name,address​)"]
doit "a,b(c)d),e,f)"
  #=> RuntimeError: parens are unbalanced
doit "a,b(c(d),e),f("
  #=> RuntimeError: parens are unbalanced, stack at end=["("]

A comma is to be split upon if and only if stack is zero when it is encountered. If it is to be split upon it is changed to a character (split_here) that is not in the string. (I used 0.chr). The string is then split on split_here.

Answer 2

This could be one approach:

"id,name,title(first_name,last_name)".split(",")[0..1] << "id,name,title(first_name,last_name)".split(",")[-2..-1].join

Creating a duplicate string and splitting them both, then combining the first two elements of the first string with the joined last two elements of the second string copy. At least in this specific scenario it would give you the desired result.

Answer 3

Updated Answer

Since the earlier answer didn't take care of all the cases as rightly pointed out in the comments, I'm updating the answer with another solution.

This approach separates the valid commas using a separator | and, later uses it to split the string using String#split.

class TokenArrayParser
  SPLIT_CHAR = '|'.freeze

  def initialize(str)
    @str = str
  end

  def parse
    separate_on_valid_comma.split(SPLIT_CHAR)
  end

  private

  def separate_on_valid_comma
    dup = @str.dup
    paren_count = 0
    dup.length.times do |idx|
      case dup[idx]
      when '(' then  paren_count += 1
      when ')' then paren_count -= 1
      when ',' then dup[idx] = SPLIT_CHAR if paren_count.zero?
      end
    end

    dup
  end
end

%w(
  id,name,title(first_name,last_name)
  id,name,title(first_name,last_name,address(street,pincode(id,code)))
  first_name,last_name,address(street,pincode(id,code)),city(name)
  a,b(c(d),e,f)
  id,name,title(first_name,last_name),pub(name,address)
).each {|str| puts TokenArrayParser.new(str).parse.inspect }

# =>
# ["id", "name", "title(first_name,last_name)"]
# ["id", "name", "title(first_name,last_name,address(street,pincode(id,code)))"]
# ["first_name", "last_name", "address(street,pincode(id,code))", "city(name)"]
# ["a", "b(c(d),e,f)"]
# ["id", "name", "title(first_name,last_name)", "pub(name,address)"]

I'm sure this can be optimized more.