JSON to Ruby Class & Struct Generator

About the JSON to Ruby

Generate Ruby classes with keyword-argument constructors, a from_hash builder and to_h, or compact Struct definitions, all with snake_case attribute names.

Key features

• Ruby classes with keyword-argument constructors
• from_hash builders that construct nested objects
• to_h methods that restore the original JSON keys
• Or compact Struct definitions (keyword_init)
• snake_case attributes; Ruby keywords made safe
• Optional values default to nil

Ruby objects from JSON

Ruby makes it easy to dig through JSON.parse hashes, but hash["customer"]["address"]["city"] gets fragile fast. Generate plain Ruby classes with readable attributes, a from_hash builder and to_h.

Example

{ "id": 1001, "price": 9.5, "tags": ["gift"], "customer": { "name": "Ada" }, "coupon": null }

class Order
  attr_accessor :id, :price, :tags, :customer, :coupon

  def initialize(id:, price:, tags:, customer:, coupon: nil)
    @id = id
    @price = price
    @tags = tags
    @customer = customer
    @coupon = coupon
  end

  def self.from_hash(h)
    new(
      id: h['id'],
      price: h['price'],
      tags: h['tags'],
      customer: Customer.from_hash(h['customer']),
      coupon: h['coupon'],
    )
  end

  def to_h
    { 'id' => @id, 'price' => @price, 'tags' => @tags, 'customer' => @customer&.to_h, 'coupon' => @coupon }
  end
end

order = Order.from_hash(JSON.parse(response.body))
order.customer.name # => "Ada"

Struct mode

Order = Struct.new(:id, :price, :tags, :customer, :coupon, keyword_init: true)

Struct mode is ideal for flat data: Order.new(**JSON.parse(json, symbolize_names: true)). The keys must match the member names, and nested hashes stay hashes.

Tips

• Ruby 3.2+: consider Data.define(...) for immutable value objects.
• Type checking: add RBS or Sorbet signatures using the attribute types shown in your JSON.
• Serialization: JSON.generate(order.to_h) turns objects back into JSON.

Related tools

Generating for another dynamic language? See JSON to Python or JSON to Elixir.

How to use the JSON to Ruby

1. Paste your data into the input box, upload a file, or click Sample to try it out.
2. Adjust the options above the editor if you need to (indentation, delimiter, and so on).
3. The Ruby appears instantly in the output panel. Any errors are shown with their line and column.
4. Click Copy to copy the result, or Download to save it as a file.