json_resource – Create Ruby objects from JSON data

class Post
  include JsonResource::Model
  
  attribute :id,          type: :integer
  attribute :body,        type: :string
  attribute :timestamp,   type: :time
  attribute :status_code, type: :integer, path: %w[status statusCode]
  attribute :status_text, type: :string,  path: %w[status statusText]
  
  has_collection :comments
end

class Comment
  include JsonResource::Model
  
  attribute :author,    type: :string
  attribute :text,      type: :string
  attribute :timestamp, type: :time
end

{
  "posts": [
    {
      "id": 123,
      "body": "Lorem ipsum",
      "timestamp": "2021-12-08T18:43:00",
      "status": {
        "statusCode": 2,
        "statusText": "published"
      },
      "comments": [
        {
          "author": "Mr. Spock",
          "text":   "Fascinating!",
          "timestamp": "2350-05-01T19:00:00"
        },
        {
          "author": "Chekov",
          "text":   "Warp 10",
          "timestamp": "2350-05-01T20:00:00"
        }
      ]
      
    }
  ]
}

posts = Post.collection_from_json(json, root: 'posts')

posts.first.id => 123
posts.first.body => 'Lorem ipsum'
posts.first.status_text => 'published'
posts.first.comments.first.author => 'Mr. Spock'

Instantiation

To instantiate collections, use collection_from_json on a JSON array.

To instantiate single objects, use from_json on a JSON hash.

Field types

Attributes can have one of the following types:

Type	Conversion	Options
:string	value
:integer	value.to_i
:float	value.to_f
:boolean	any of [true, 1, '1', 't', 'T', 'true', 'TRUE', 'on', 'ON']
:decimal	direct, or to_d	:precision, :scale
:date	Date.parse
:time	Time.parse

Extracting data

Sometimes, APIs return data wrapped within arrays of hashes of arrays etc:

{
  "data": [
    {
      "status": "ok"
    },
    {
      "planets": [
        {
          "name": "Earth",
          "mass": 5.9722E+24,
          "orbit": 1.000
        },
        {
          "name": "Jupiter",
          "mass": 1.8990E+27,
          "orbit": 5.205
        }
      ]
    }
  ]
}

class Planet
  include JsonResource::Model
  
  attribute :name, type: :string
  attribute :mass, type: :decimal, precision: 10, scale: 4
end

To dig for this data, a call-sequence can be provided as the root option.

planets = Planet.collection_from_json(json, root: %w[data [1] planets])