What is an elegant way of modifying hashes inside an array within a nested hash in Ruby

Question

I would like to transform this

def some_process(k,v)
    return "#{v}_#{k}"
end

a_hash = {
    "i_love_hashes" => {
        "thing" => 20,
        "other_thing" => "0",
        "yet_another_thing" => "i disagree",
        "_peculiar_thing" => [
            {"count" => 30,
            "name" => "freddie"},
            {"count" => 15,
            "name" => "johhno"},
            {"count" => 12,
            "name" => "mohammed"},
        ]
    },
    "as_do_i" => {
       "thing" => 10,
       "other_thing" => "2",
       "yet_another_thing" => "i strongly agree",
       "_peculiar_thing" => [
           {"count" => 10,
           "name" => "frodo"},
           {"count" => 4,
           "name" => "bilbo"},
           {"count" => 2,
           "name" => "elizabeth"},
       ] 
    }
}

into this

{
"i_love_hashes"=>{
    "thing"=>20, 
    "other_thing"=>"0", 
    "yet_another_thing"=>"i disagree", 
    "_peculiar_thing"=> [
        {"count"=>30, "name"=>"freddie", :sinister_name=>"freddie_i_love_hashes"}, 
        {"count"=>15, "name"=>"johhno", :sinister_name=>"johhno_i_love_hashes"}, 
        {"count"=>12, "name"=>"mohammed", :sinister_name=>"mohammed_i_love_hashes"}
        ]}, 
"as_do_i"=>{
    "thing"=>10, 
    "other_thing"=>"2", 
    "yet_another_thing"=>"i strongly agree", 
    "_peculiar_thing"=>[
        {"count"=>10, "name"=>"frodo", :sinister_name=>"frodo_as_do_i"},
        {"count"=>4, "name"=>"bilbo", :sinister_name=>"bilbo_as_do_i"}, 
        {"count"=>2, "name"=>"elizabeth", :sinister_name=>"elizabeth_as_do_i"}
        ]
    }
}

this is the code I am currently using to achieve this

a_hash.each_with_object({}) do |(k,v),o|
  o.merge!({k =>
      v.each_with_object({}) do |(a,b),g|
        g.merge!({ a =>
          (b.is_a?(Array) ? b.collect {|x| x.merge({sinister_name: (some_process k, x["name"])})} : b)
          })
      end
    })
end

Ignoring the specific details of what is being returned by "some_process" (what is important is that it depends on the outer most key and the inner name values, in this example), are there any alternatives that would be considered more elegant?

@Phlip I would almost always use inject for this but the second answer [here](http://stackoverflow.com/questions/5481009/why-is-enumerableeach-with-object-deprecated) gives a credible reason why each_with_object is valid. — Mike H-R, Nov 22 '13 at 00:25
It turns out, http://stackoverflow.com/questions/5481009/why-is-enumerableeach-with-object-deprecated , that `each_with_object` is merely `inject` without the need to return the hash (in your case) at the end of each block. — Phlip, Nov 25 '13 at 01:00
given I can write your algorithm as `a_hash.each do |key, value| value['_peculiar_thing'].map do |h| h.merge! :sinister_name => "#{ h['name'] }_i_love_hashes" end end`, if I don't mind stomping on your input `a_hash`, you could also dispense with `each_with_object` altogether and merely deep-clone `a_hash` before you start. if you mind it gets stomped on. — Phlip, Nov 25 '13 at 01:02

score 0 · Answer 1 · answered Nov 22 '13 at 08:50

0

Why not do a recursive function?

def add_siniter(hash) 
  hash[:siniter_name] = "#{hash['name']}_i_love_hashes"
  hash
end

def format_hash(item)
  case item
    when Hash  then item.keys.each{|key| format_hash(item[key])}
    when Array then item.map!{|h| add_siniter(h)}
  end
end

format_hash(a_hash)

answered Nov 22 '13 at 08:50

hirolau

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While I like the idea of a recursive method, the top level keys would need to be passed down, along with a depth parameter, to make it work, in this case. – OhNoez Woez Nov 24 '13 at 22:30
Also, the format_hash method you've provided only appears to return an array of the two top-level keys, when run with the provided hash. – OhNoez Woez Nov 24 '13 at 22:31

What is an elegant way of modifying hashes inside an array within a nested hash in Ruby

1 Answers1