Mapping an array of hashes to a keyed hash in Ruby

Question

I have an array of hashes that looks like this:

   array= [
      {
        "id"=> 101,
        "first_name"=> "xxx",
        "last_name"=> "G",
        "email"=> "[email protected]",
        "phone_number"=> "555-555-5555"
      },
      {
        "id"=> 102,
        "first_name"=> "Jen",
        "last_name"=> "P",
        "email"=> "[email protected]",
        "phone_number"=> "555-555-5555"
      }
    ]

I want to convert it to a hash that looks like this:

   array = {
          "101"=> 
          {
            "first_name"=> "xxx",
            "last_name"=> "G",
            "email"=> "[email protected]",
            "phone_number"=> "555-555-5555"
          },
          "102"=>
          {
            "first_name"=> "Jen",
            "last_name"=> "P",
            "email"=> "[email protected]",
            "phone_number"=> "555-555-5555"
          }
       }

I have tried this but it does not work:

    array.each do |a|
      a.map{|x| x[:id]}
    end

How can I do this in Ruby? I am looking at the map function, but not sure how to implement it in this case. Please help!

anyway, your array of hashes have the wrong syntax, it's not a Ruby hash, it's looks like javascript json — Roman Kiselenko
– Roman Kiselenko, Commented Jul 13, 2015 at 7:45
@Зелёный Okay thanks for pointing out. I am using the json library to convert this to a ruby hash. but my question still remains — gazubi
– gazubi, Commented Jul 13, 2015 at 7:47
This is very similar to the output of group_by as in array.group_by{|a| a[:id]}. — Mark Thomas
– Mark Thomas, Commented Jul 13, 2015 at 9:33

Roman Kiselenko · Accepted Answer · 2015-07-13 08:48:51Z

3

This works(desctructive):

>> Hash[array.map { |x| [x.delete("id"), x] }]
=>{
    101=>{
        "first_name"=>"xxx",
        "last_name"=>"G",
        "email"=>"[email protected]",
        "phone_number"=>"555-555-5555"
    },
    102=>{
        "first_name"=>"Jen",
        "last_name"=>"P",
        "email"=>"[email protected]",
        "phone_number"=>"555-555-5555"
    }
}

edited Jul 13, 2015 at 8:48

answered Jul 13, 2015 at 7:52

Roman Kiselenko

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2 Comments

tompave Over a year ago

This doesn't really return what the OP asked. It returns another Array of hashes, and it just wraps each original hash into a further hash. Other users have provided the right solution.

D-side Over a year ago

Since Ruby 2.1 it is also possible to use x.to_h instead of Hash[x]. Mostly aesthetic difference.

Gagan Gami · Accepted Answer · 2015-07-13 09:15:28Z

3

Try this:

array_h = Hash.new
array.each{|a| array_h[a["id"]] = a.reject{|e| e=='id' }}

#Output of array_h:
{
  101=>
    {
      "first_name"=>"xxx", 
      "last_name"=>"G", 
      "email"=>"[email protected]", 
      "phone_number"=>"555-555-5555"
    }, 
  102=>
    {
      "first_name"=>"Jen", 
      "last_name"=>"P", 
      "email"=>"[email protected]", 
      "phone_number"=>"555-555-5555"
    }
}

Note: This will not modify your original Array.

edited Jul 13, 2015 at 9:15

answered Jul 13, 2015 at 7:57

Gagan Gami

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Comments

Amadan · Accepted Answer · 2015-07-13 08:06:37Z

0

Non-destructive variant (preserves array) while removing "id":

{}.tap { |h| array.each { |a| nh = a.dup; h[nh.delete('id')] = nh } }
# => {101=>{"first_name"=>"xxx", "last_name"=>"G", "email"=>"[email protected]", "phone_number"=>"555-555-5555"}, 102=>{"first_name"=>"Jen", "last_name"=>"P", "email"=>"[email protected]", "phone_number"=>"555-555-5555"}} 
array
# => [{"id"=>101, "first_name"=>"xxx", "last_name"=>"G", "email"=>"[email protected]", "phone_number"=>"555-555-5555"}, {"id"=>102, "first_name"=>"Jen", "last_name"=>"P", "email"=>"[email protected]", "phone_number"=>"555-555-5555"}]

answered Jul 13, 2015 at 8:06

Amadan

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