Transforming an array of arrays to an array of hashes in Ruby

Question

I'm trying to transform a two dimensional array to an array of hashes. Here is my array:

[[8765, 105191, 2.0, 1582.1], [4321, 62870, 2.0, 603.24], [1234, 62870, 2.0, 500.24]]

I'm trying to transform this to an array of hash values. Something like this:

[{"sales_user_id"=>"8765", "user_id"=>"105191", "month"=>"2", "sum"=>"1582.1"},
{"sales_user_id"=>"4321", "user_id"=>"62870", "month"=>"2", "sum"=>"603.24"},
{"sales_user_id"=>"1234", "user_id"=>"62870", "month"=>"2", "sum"=>"500.24"}]

I'm breaking down each array and assigning a key to the values in the array. I'm still a little new to ruby and I'm not sure where to start.

Answer 1

This is pretty straightforward with Enumerable#zip :

values = [ [ 8765, 105191, 2.0, 1582.1 ],
           [ 4321,  62870, 2.0, 603.24 ],
           [ 1234,  62870, 2.0, 500.24 ] ]
keys = %w[sales_user_id user_id month sum]

p values.map {|arr| keys.zip(arr).to_h }
# => [ { "sales_user_id" => 8765, "user_id" => 105191, "month" => 2.0, "sum" =>  1582.1 },
#      { "sales_user_id" => 4321, "user_id" =>  62870, "month" => 2.0, "sum" =>  603.24 },
#      { "sales_user_id" => 1234, "user_id" =>  62870, "month" => 2.0, "sum" =>  500.24 } ]

Answer 2

arr = [[8765, 105191, 2.0, 1582.1 ],
       [4321, 62870,  2.0,  603.24],
       [1234, 62870,  2.0,  500.24]]

keys = ["sales_user_id", "user_id", "month", "sum"]

First way

[keys].product(arr).map { |a| a.transpose.to_h }
  #=> [{"sales_user_id"=>8765, "user_id"=>105191, "month"=>2.0, "sum"=>1582.1},
  #    {"sales_user_id"=>4321, "user_id"=> 62870, "month"=>2.0, "sum"=>603.24},
  #    {"sales_user_id"=>1234, "user_id"=> 62870, "month"=>2.0, "sum"=>500.24}]

The steps:

enum = [keys].product(arr)
  #=> #<Enumerator:
  #     [
  #      [["sales_user_id", "user_id", "month", "sum"], [8765, 105191, 2.0, 1582.1]],
  #      [["sales_user_id", "user_id", "month", "sum"], [4321, 62870, 2.0, 603.24]],
  #      [["sales_user_id", "user_id", "month", "sum"], [1234, 62870, 2.0, 500.24]]
  #     ]:map> 

a = enum.next
  #=> [["sales_user_id", "user_id", "month", "sum"], [8765, 105191, 2.0, 1582.1]]
c = a.transpose
  #=> [["sales_user_id", 8765], ["user_id", 105191], ["month", 2.0], ["sum", 1582.1]] 
c.to_h
  #=> {"sales_user_id"=>8765, "user_id"=>105191, "month"=>2.0, "sum"=>1582.1} 

a = enum.next
  #=> [["sales_user_id", "user_id", "month", "sum"], [4321, 62870, 2.0, 603.24]] 
c = a.transpose
  #=> [["sales_user_id", 4321], ["user_id", 62870], ["month", 2.0], ["sum", 603.24]] 
c.to_h
  #=> {"sales_user_id"=>4321, "user_id"=>62870, "month"=>2.0, "sum"=>603.24} 

a = enum.next
  #=> [["sales_user_id", "user_id", "month", "sum"], [1234, 62870, 2.0, 500.24]] 
c = a.transpose
  #=> [["sales_user_id", 1234], ["user_id", 62870], ["month", 2.0], ["sum", 500.24]] 
c.to_h
  #=> {"sales_user_id"=>1234, "user_id"=>62870, "month"=>2.0, "sum"=>500.24} 

Second way

arr.map do |a|
  ad = a.dup
  { "sales_user_id"=>ad.shift, "user_id"=>ad.shift, "month"=>ad.shift, "sum"=>ad.shift }
end
  #=> [{"sales_user_id"=>8765, "user_id"=>105191, "month"=>2.0, "sum"=>1582.1},
  #    {"sales_user_id"=>4321, "user_id"=> 62870, "month"=>2.0, "sum"=>603.24},
  #    {"sales_user_id"=>1234, "user_id"=> 62870, "month"=>2.0, "sum"=>500.24}]

Answer 3

Also consider using a Struct if you have a fixed set of values per object. Can be used pretty much as a hash.

User = Struct.new(:sales_user_id, :user_id, :month, :sum)

array = [[8765, 105191, 2.0, 1582.1], [4321, 62870, 2.0, 603.24], [1234, 62870, 2.0, 500.24]]

users = array.map {|values| User.new *values}

p users #=> [#<struct User sales_user_id=8765, user_id=105191, month=2.0, sum=1582.1>, #<struct User sales_user_id=4321, user_id=62870, month=2.0, sum=603.24>, #<struct User sales_user_id=1234, user_id=62870, month=2.0, sum=500.24>]


p users.first.user_id    #=> 105191
p users.first['user_id'] #=> 105191
p users.first[:user_id]  #=> 105191

Answer 4

Here's one way to do it that uses .collect to iterate over the outer array and construct a hash for each inner array:

values = [[8765, 105191, 2.0, 1582.1],
          [4321, 62870, 2.0, 603.24],
          [1234, 62870, 2.0, 500.24]]

result = values.collect do |array|
  {
    "sales_user_id" => array[0].to_s,
    "user_id" => array[1].to_s,
    "month" => array[2].to_i.to_s,
    "sum" => array[3].to_s
  }
end

result :

[{"sales_user_id"=>"8765", "user_id"=>"105191", "month"=>"2", "sum"=>"1582.1"},
 {"sales_user_id"=>"4321", "user_id"=>"62870", "month"=>"2", "sum"=>"603.24"},
 {"sales_user_id"=>"1234", "user_id"=>"62870", "month"=>"2", "sum"=>"500.24"}]

It also uses .to_s and .to_i to coerce the result into the values in the question (like 8765 to "8765" and 2.0 to "2" ).