Creating nested hashes from nested array

Question

I'd like to turn a response from the following query:

sites = Site.find(request.review_sites).pluck(:id, :location_id, :site_name, :review_url,:created_at)

which provided output like below,

[
  [
    50,
    2,
    "google",
    "https://search.google.com/local/writereview?placeid=000000001flMRNRVr8YpJWuY",
    Thu, 06 Dec 2018 20:18:29 UTC +00:00
  ],
  [
    51,
    2,
    "facebook",
    "https://www.facebook.com/biz/reviews/?ref=page_internal",
    Thu, 06 Dec 2018 20:18:35 UTC +00:00
  ]
]

into a nested hash like the following (which I'll be working with as JSON quite a bit later):

{
  :google => {
    :id => 50,
    :create_at => "2018-12-06T20:18:29.651Z",
    :site_name => "google",
    :review_url => "https://search.google.com/local/writereview?placeid=00000000001flMRNRVr8YpJWuY",
    :location_id => 2
  },
  :facebook => {
    :id => 51,
    :create_at => "2018-12-06T20:18:35.639Z",
    :site_name => "facebook",
    :review_url => "https://www.facebook.com/biz/reviews/?ref=page_internal",
    :location_id => 2
  }
}

I realize this is a duplicate, but I'm struggling to implement some answers given. I'm struggling to do this programmatically, so any help would be appreciated.

It seems your example doesn't have a valid syntax. Could you clarify that? — Sebastián Palma
– Sebastián Palma, Commented Dec 7, 2018 at 10:51
I updated the question to show what I wanted (is that where you meant it was invalid syntax?), but I believe I solved the issue below. — Rich
– Rich, Commented Dec 7, 2018 at 10:53
@Rich You have displayed your array in a format that is output by some libraries, but neverthess non-standard, and not liked by so many people. It is better to use the standard inspection form, as I changed into. — sawa
– sawa, Commented Dec 7, 2018 at 11:20
What is Site, what is pluck? Ruby does not have such things. — sawa
– sawa, Commented Dec 7, 2018 at 11:22
Check answer I posted, which will better one for you to render data — ray
– ray, Commented Dec 7, 2018 at 11:40

sawa · Accepted Answer · 2018-12-07 11:29:02Z

2

Let your array be array. In Ruby < 2.6, you can get the hash by:

array.map do
  |id, location_id, site_name, review_url, create_at|
  [site_name.to_i, {
    id: id,
    create_at: create_at,
    site_name: site_name,
    review_url: review_url,
    location_id: location_id,
  }].to_h
end

In Ruby 2.6, you can get it by:

array.to_h do
  |id, location_id, site_name, review_url, create_at|
  [site_name.to_i, {
    id: id,
    create_at: create_at,
    site_name: site_name,
    review_url: review_url,
    location_id: location_id,
  }]
end

answered Dec 7, 2018 at 11:29

sawa

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1 Comment

Rich Over a year ago

Whoa! That's a really nice feature coming with Ruby 2.6! While I was trying to sort this out, I was wondering what the reason was Ruby didn't have some way to do array.to_h Thanks for sharing this! Unfortunately, I'm still running 2.5.3, but will keep this in mind!

ray · Accepted Answer · 2018-12-07 11:39:00Z

I got what you are looking for,

Try folowing,

sites = Site.find(request.review_sites)
          .as_json(only: [:id, :location_id, :site_name, :review_url,:created_at])
          .group_by { |x| x['site_name'] }

Output look likes,

{
  'google' => [
    {
      'id' => 50,
      'create_at' => "2018-12-06T20:18:29.651Z",
      'site_name' => "google",
      'review_url' => "https://search.google.com/local/writereview",
      'location_id' => 2
    },
    {
      'id' => 52,
      'create_at' => "2018-14-06T20:18:29.651Z",
      'site_name' => "google",
      'review_url' => "https://search.google.com/local/readerview",
      'location_id' => 3
    }
  ],
  'facebook' => [
    {
      'id' => 51,
      'create_at' => "2018-12-06T20:18:35.639Z",
      'site_name' => "facebook",
      'review_url' => "https://www.facebook.com/biz/reviews/?ref=page_internal",
      'location_id' => 2
    }
  ]
}

DannyB · Accepted Answer · 2018-12-07 11:08:28Z

1

In your case pluck might not be the right tool for the job.

If you have control over it, I would change it to something like the below (separated to several logical lines just for convenience).

collection = Site.find(request.review_sites)
columns = [:id, :location_id, :site_name, :review_url, :created_at]
sites = collection.select(columns).map { |v| [v.id, v.attributes] }.to_h

Using select returns the attributes you need as a hash, and then you can map it however you like. Converting to json would then be a matter of sites.to_json.

answered Dec 7, 2018 at 11:08

DannyB

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3 Comments

Rich Over a year ago

I was under the impression using find + pluck is more efficient than mapping? Either way, this is more readable. Thanks for your answer!

DannyB Over a year ago

Note that the map is only performed after we already selected only the specific columns, and not the entire object - so I think performance wise, we did not sacrifice much, if at all. I might be wrong, but in any case, accessing the response by its array index (like in your original answer) seems like something I would want to avoid.

Rich Over a year ago

Ah, I understand - that makes sense to avoid accessing via array index. Thank you.

Rich · Accepted Answer · 2018-12-07 10:51:40Z

0

I solved it thanks to this response by @dcarneiro

Here is how I created nested hashes out of nested arrays for anyone who finds this.

      review_sites = Site.find(request.review_sites).pluck(:id, :location_id, :site_name, :review_url,:created_at)
      sites_hash = Hash[review_sites.map do |site| 
        [site[2], Hash['id', site[0], 'location_id', site[1], 'site_name', site[2], 'review_url', site[3], 'create_at', site[4] ]]
      end]

answered Dec 7, 2018 at 10:51

Rich

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3 Comments

DannyB Over a year ago

But this is not a very robust way to handle it. If the part of the code that uses pluck is under your control, then I would replace it with select([:id, :location_id, :site_name, :review_url,:created_at]) - which will give you an array of hashes that is easier to process to the structure you need using map.

Alex Suslyakov Over a year ago

@Rich I'd recommend moving keys to a constant (if they're stable of course) and use zip. sites_hash = KEYS.zip(review_sites).to_h . (ruby-doc.org/core-2.5.3/Enumerable.html#method-i-zip)

Rich Over a year ago

@mbuechmann I answered my own question before anyone else answered. Their answers were helpful and appreciated because I have now learnt a better way to implement something like this than how I did it.

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