Create JSON of one dimension Ruby

I want to have this:

["(GKA) GOROKA, GOROKA, PAPUA NEW GUINEA"]

instead of:

[ [ "(GKA)", "GOROKA", "GOROKA", "PAPUA NEW GUINEA" ] ]

I have this code so far:

@aeropuertos = ""
    f = File.open("./public/aeropuertos/aeropuertos.cvs", "r")
    f.each_line { |line|
      fields = line.split(':')

      if (fields[2] == "N/A")
        @line =  "(" << fields[1] << ")" << ",," << fields[3] << "," << fields[4]
      else
        @line =  "(" << fields[1] << ")"  << "," << fields[2] << "," << fields[3] << "," << fields[4]
      end
      @aeropuertos += @line << "\n"
    }
    return CSV.parse(@aeropuertos).to_json

What should I do?

@aeropuertos = ""

f = File.open("./public/aeropuertos/aeropuertos.cvs", "r")
f.each_line { |line|
  fields = line.split(':')

  if (fields[2] == "N/A")
    @line =  "(" << fields[1] << ")" << ",," << fields[3] << "," << fields[4]
  else
    @line =  "(" << fields[1] << ")"  << "," << fields[2] << "," << fields[3] << "," << fields[4]
  end
  @aeropuertos += @line << "\n"
}
res = []
CSV.parse(@aeropuertos).each do |c|
    res << c.join(',')
end
return res.to_json

There's no need for the CSV parser. Just create the structure you want as you read each line. That is, instead of making a large string in @aeropuertos and parsing it with a CSV parser, make @aeropuertos an array, and add each @line to the array.

So, instead of this:

@aeropuertos += @line << "\n"

Do this:

@aeropuertos << @line

But be sure to say this at the beginning:

@aeropuertos = []