Ruby hashes group by multiple value

Question

I have multiple hashes who looks like this:

[{"name" => "name1", "folder" => "folder1", id => 1 },

{"name" => "name1", "folder" => "folder1", id => 2 },

{"name" => "name1", "folder" => "folder2", id => 3},

{"name" => "name2", "folder" => "folder1", id => 4}]

And my goal is to have something who looks like this:

   {"name1" => 
    [{"folder1" =>
      [{"name" => "name1", "folder" => "folder1", id => 1 },
       {"name" => "name1", "folder" => "folder1", id => 2 }] }
     {"folder2" => 
       [{"name" => "name1", "folder" => "folder2", id => 3}] }]

    {"name2" => 
     [{"folder 1" => 
       [{"name" => "name2", "folder" => "folder1", id => 4}] }] }

I didn't find a proper solution who give exactly this kind or a similar result for now.

Edit: i tried that and many others but never found the way of having two level's deep hashes a.group_by{|line| line["name"]}.each_value {|v| v.map{|line| line["folder"]}} a.group_by{|line| line["name"]}.each_value {|v| v.map{|line| line["folder"]}}

Answer 1

This seems to do what you want :

transformed_hash = initial_hash
  .group_by { |x| x['name'] }
  .map { |k, v| [k, v.group_by{ |x| x['folder'] }] }
  .to_h

Answer 2

a = [{"name" => "name1", "folder" => "folder1", 'id' => 1 },
{"name" => "name1", "folder" => "folder1", 'id' => 2 },
{"name" => "name1", "folder" => "folder2", 'id' => 3},
{"name" => "name2", "folder" => "folder1", 'id' => 4}]

a.group_by { |c| c['name'] }.map do |key, value| 
   [key, [value.group_by { |c| c['folder']}]]
end.to_h

 => {"name1"=>
       [{"folder1"=>[
          {"name"=>"name1", "folder"=>"folder1", "id"=>1},
          {"name"=>"name1", "folder"=>"folder1", "id"=>2}],   
         "folder2"=>[
          {"name"=>"name1", "folder"=>"folder2", "id"=>3}]}],    
     "name2"=>
       [{"folder1"=>[
          {"name"=>"name2", "folder"=>"folder1", "id"=>4}]}]
     }