Turn array into array of hashes (Ruby)

Question

I'm struggling on a task that consists of turning an array into an array of hashes with children.

Basically, I need to create a hierarchical html table of content from an array of headings.

Here is the initial array:

- !ruby/object:Prismic::Fragments::StructuredText::Block::Heading
  text: Quelles espèces de dauphins peut-on voir en Martinique ?
  level: 2
- !ruby/object:Prismic::Fragments::StructuredText::Block::Heading
  text: Dauphin de Fraser
  level: 3
- !ruby/object:Prismic::Fragments::StructuredText::Block::Heading
  text: Dauphin tacheté pantropical
  level: 3
- !ruby/object:Prismic::Fragments::StructuredText::Block::Heading
  text: Dauphin d’Électre
  level: 3
- !ruby/object:Prismic::Fragments::StructuredText::Block::Heading
  text: Le grand dauphin
  level: 3
- !ruby/object:Prismic::Fragments::StructuredText::Block::Heading
  text: Globicéphale tropical
  level: 3
- !ruby/object:Prismic::Fragments::StructuredText::Block::Heading
  text: Les meilleurs spots pour voir les dauphins en Martinique
  level: 2
- !ruby/object:Prismic::Fragments::StructuredText::Block::Heading
  text: Conditions idéales pour l’observation des dauphins en Martinique
  level: 2
- !ruby/object:Prismic::Fragments::StructuredText::Block::Heading
  text: Comment se déroule cette balade en mer ?
  level: 2

Basically, I need the previous array to look like this array of hashes :

[
  {
    "text" => "Quelles espèces de dauphins peut-on voir en Martinique ?",
    "level" => 2,
    "children" => [
      {
        "text" => "Dauphin de Fraser",
        "level" => 3,
        "children" => []
      },
      {
        "text" => "Dauphin tacheté pantropical",
        "level" => 3,
        "children" => []
      },
      {
        "text" => "Dauphin d’Électre",
        "level" => 3,
        "children" => []
      },
      {
        "text" => "Le grand dauphin",
        "level" => 3,
        "children" => []
      },
      {
        "text" => "Globicéphale tropical",
        "level" => 3,
        "children" => []
      }
    ]
  },
  {
    "text" => "Les meilleurs spots pour voir les dauphins en Martinique",
    "level" => 2,
    "children" => []
  },
  {
    "text" => "Conditions idéales pour l’observation des dauphins en Martinique",
    "level" => 2,
    "children" => []
  },
  {
    "text" => "Comment se déroule cette balade en mer ?",
    "level" => 2,
    "children" => []
  }
]

So, an item needs to be included in the previous item if its level value is greater than the previous item. Allowing it to create a hierarchical array of hashes.

Any help on that ? Thanks in advance !

Les Nightingill · Accepted Answer · 2021-08-13 19:21:46Z

1

Ruby's inject method should solve your problem:

array.inject([]) do |ar,item|
  collection = case item.level
               when 2
                 ar
               when 3
                 ar[-1][:children]
               when 4
                 ar[-1][:children][-1][:children]
               when 5
                 ar[-1][:children][-1][:children][-1][:children]
               # etc..
               end

    collection.push {text: item.text,
                     level: item.level,
                     children: []}
  
  ar
end

where is array is the array of ruby objects you listed in your post.

edited Aug 13, 2021 at 19:21

answered Aug 13, 2021 at 17:27

Les Nightingill

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5 Comments

user12178999 Over a year ago

Okay this looks about right, thanks ! One thing, there can be more that 2 and 3 levels... It can be 4, 5 and 6 as well. How should I handle that ? I guess I have to modify if item.level == 2...

Les Nightingill Over a year ago

edited my answer... does that do what you need?

max pleaner Over a year ago

There is certainly a way to do this without hard coding numbers

max pleaner Over a year ago

You should be able to replace that whole case statement with this: collection = ar; (item.level - 2).times { collection = collection[-1][:children] }

user12178999 Over a year ago

@maxpleaner you are a literal god. No idea how this works but it works. I should dig in it a little later. Thanks a lot (wo)man !

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