ex.rb

require 'transproc/all'
require 'json'

json = <<-EOS
{
  "links": {
    "self": "http://example.com/posts",
    "next": "http://example.com/posts?page[offset]=2",
    "last": "http://example.com/posts?page[offset]=10"
  },
  "data": [{
    "type": "posts",
    "id": "1",
    "title": "JSON API paints my bikeshed!",
    "links": {
      "self": "http://example.com/posts/1",
      "author": {
        "self": "http://example.com/posts/1/links/author",
        "related": "http://example.com/posts/1/author",
        "linkage": { "type": "people", "id": "9" }
      },
      "comments": {
        "self": "http://example.com/posts/1/links/comments",
        "related": "http://example.com/posts/1/comments",
        "linkage": [
          { "type": "comments", "id": "5" },
          { "type": "comments", "id": "12" }
        ]
      }
    }
  }],
  "included": [{
    "type": "people",
    "id": "9",
    "first-name": "Dan",
    "last-name": "Gebhardt",
    "twitter": "dgeb",
    "links": {
      "self": "http://example.com/people/9"
    }
  }, {
    "type": "comments",
    "id": "5",
    "body": "First!",
    "links": {
      "self": "http://example.com/comments/5"
    }
  }, {
    "type": "comments",
    "id": "12",
    "body": "I like XML better",
    "links": {
      "self": "http://example.com/comments/12"
    }
  }]
}
EOS

# compose transformation functions
include Transproc::Helper

Transproc.register(:recursive_symbolize_keys, t(:hash_recursion, t(:symbolize_keys)))

transformation = t(:recursive_symbolize_keys) + t(:map_values, t(:is, ::Array, t(:map_array, t(:recursive_symbolize_keys))))

pp transformation.call(JSON.parse(json))
{:links=>
  {:self=>"http://example.com/posts",
   :next=>"http://example.com/posts?page[offset]=2",
   :last=>"http://example.com/posts?page[offset]=10"},
 :data=>
  [{:type=>"posts",
    :id=>"1",
    :title=>"JSON API paints my bikeshed!",
    :links=>
     {:self=>"http://example.com/posts/1",
      :author=>
       {:self=>"http://example.com/posts/1/links/author",
        :related=>"http://example.com/posts/1/author",
        :linkage=>{:type=>"people", :id=>"9"}},
      :comments=>
       {:self=>"http://example.com/posts/1/links/comments",
        :related=>"http://example.com/posts/1/comments",
        :linkage=>
         [{"type"=>"comments", "id"=>"5"},
          {"type"=>"comments", "id"=>"12"}]}}}],
 :included=>
  [{:type=>"people",
    :id=>"9",
    :"first-name"=>"Dan",
    :"last-name"=>"Gebhardt",
    :twitter=>"dgeb",
    :links=>{:self=>"http://example.com/people/9"}},
   {:type=>"comments",
    :id=>"5",
    :body=>"First!",
    :links=>{:self=>"http://example.com/comments/5"}},
   {:type=>"comments",
    :id=>"12",
    :body=>"I like XML better",
    :links=>{:self=>"http://example.com/comments/12"}}]}