无法找出哈希红宝石数组

Question

I am trying to turn an array of arrays into an array of hashes. Could someone try to explain what I am exactly doing wrong here? The first array within the array of arrays becomes the keys for the hash. I can get the method to return one hash or even three of the same hashes. But I can't get it return each different new hash within the final array.

table_data = [
  ["first_name", "last_name", "city", "state"],
  ["Elisabeth", "Gardenar", "Toledo", "OH"],
  ["Jamaal", "Du", "Sylvania", "OH"],
  ["Kathlyn", "Lavoie", "Maumee", "OH"]
]


def convert_table(table_array)
  hash = {}
  final_array = []
  headers_array = table_array.shift

  table_array.each_index do |x|
    i = 0
    until i == headers_array.length
      hash[headers_array[i]] = table_array[x][i]
      final_array << hash
      i += 1
    end
  end
  final_array
end

p convert_table(table_data)

#END GOAL
[ { "first_name" => "Elisabeth", "last_name" => "Gardenar", "city" => "Toledo", "state" => "OH" },
{ "first_name" => "Jamaal", "last_name" => "Du", "city" => "Sylvania", "state"    => "OH" },
{ "first_name" => "Kathlyn", "last_name" => "Lavoie", "city" => "Maumee", "state" => "OH" }

Answer 1

Pair up keys (in table_data[0] and values (each other row in table_data ) using zip , and map them to a hash:

table_data[1..-1].map { |values| Hash[table_data[0].zip(values)] }

EDIT: The part that doesn't work in your case is having one single hash that you keep reusing. When you do final_array << hash , it doesn't add a snapshot of the hash as it is then; it adds a reference to it. Thus, you don't have an array of three hashes, you have an array with three references to the same hash. You could avoid it by doing final_array << hash.clone to actually take a snapshot; or (much simpler) just make a new hash in each iteration of the loop (move hash = {} into the table_array.each_index loop).

Answer 2

As @Amadan has diagnosed your problem, I will suggest a more "Ruby-like" approach.

keys, *data = table_data
  #=> [["first_name", "last_name", "city", "state"],
  #    ["Elisabeth", "Gardenar", "Toledo", "OH"],
  #    ["Jamaal", "Du", "Sylvania", "OH"],
  #    ["Kathlyn", "Lavoie", "Maumee", "OH"]
  #   ]
keys
  #=> ["first_name", "last_name", "city", "state"] 
data
  #=> [["Elisabeth", "Gardenar", "Toledo", "OH"],
  #    ["Jamaal", "Du", "Sylvania", "OH"],
  #    ["Kathlyn", "Lavoie", "Maumee", "OH"]
  #   ] 

[keys].product(data).map { |pair| pair.transpose.to_h }
  #=> [{"first_name"=>"Elisabeth", "last_name"=>"Gardenar", "city"=>"Toledo", 
  #       "state"=>"OH"},
  #    {"first_name"=>"Jamaal", "last_name"=>"Du", "city"=>"Sylvania",
  #       "state"=>"OH"},
  #    {"first_name"=>"Kathlyn", "last_name"=>"Lavoie", "city"=>"Maumee",
  #       "state"=>"OH"}
  #   ] 

The steps are as follows.

a = [keys].product(data)
  #=> [[["first_name", "last_name", "city", "state"],
  #     ["Elisabeth", "Gardenar", "Toledo", "OH"]
  #    ],
  #    [["first_name", "last_name", "city", "state"],
  #     ["Jamaal", "Du", "Sylvania", "OH"]],
  #    [["first_name", "last_name", "city", "state"],
  #     ["Kathlyn", "Lavoie", "Maumee", "OH"]
  #    ]
  #   ] 

The first element of a is passed to map , the block variable pair is assigned and the block calculation is performed.

pair = a.first
  #=> [["first_name", "last_name", "city", "state"],
  #    ["Elisabeth", "Gardenar", "Toledo", "OH"]
  #   ] 
b = pair.transpose
  #=> [["first_name", "Elisabeth"],
  #    ["last_name", "Gardenar"],
  #    ["city", "Toledo"],
  #    ["state", "OH"]
  #   ] 
g = b.to_h
  #=> {"first_name"=>"Elisabeth", "last_name"=>"Gardenar", "city"=>"Toledo",
  #      "state"=>"OH"} 

Therefore, a.first is mapped to g . The remaining calculations are similar.

Answer 3

Your question has been properly answered by @CarySwoveland and @Amadan.

I'd just like to add that your table basically looks like a CSV table with header.

If your table_data does come from a file, you might as well read it directly with CSV :

csv_table = "first_name,last_name,city,state
Elisabeth,Gardenar,Toledo,OH
Jamaal,Du,Sylvania,OH
Kathlyn,Lavoie,Maumee,OH"

require 'csv'

CSV.parse(csv_table, headers: true).each do |row|
  p row
end

It outputs

#<CSV::Row "first_name":"Elisabeth" "last_name":"Gardenar" "city":"Toledo" "state":"OH">
#<CSV::Row "first_name":"Jamaal" "last_name":"Du" "city":"Sylvania" "state":"OH">
#<CSV::Row "first_name":"Kathlyn" "last_name":"Lavoie" "city":"Maumee" "state":"OH">

You can work CSV::Row as with an Hash. If you really want a Hash, you can use row.to_h :

{"first_name"=>"Elisabeth", "last_name"=>"Gardenar", "city"=>"Toledo", "state"=>"OH"}
{"first_name"=>"Jamaal", "last_name"=>"Du", "city"=>"Sylvania", "state"=>"OH"}
{"first_name"=>"Kathlyn", "last_name"=>"Lavoie", "city"=>"Maumee", "state"=>"OH"}