user ids from Redmine's memberships JSON

redmine_memberships_user_ids.rb

require 'json'

json = <<JSON
  {
    "memberships": [
      {
        "id": 3786,
        "project": {
          "id": 295,
          "name": "Web Pública - UK"
        },
        "user": {
          "id": 83,
          "name": "Miriam"
        },
        "roles": [
          {
            "id": 3,
            "name": "Jefe de proyecto"
          }
        ]
      },
      {
        "id": 4111,
        "project": {
          "id": 295,
          "name": "Web Pública - UK"
        },
        "user": {
          "id": 157,
          "name": "Beatriz"
        },
        "roles": [
          {
            "id": 3,
            "name": "Jefe de proyecto"
          }
        ]
      }
    ],
    "total_count": 12,
    "offset": 0,
    "limit": 25
  }
JSON
hash = JSON.parse(json)
puts hash['memberships'].inject({}) {|sum, elem| sum[elem['user']['id']] = elem['user']['name']; sum}