Ruby implementation of OpenAI structured outputs

ruby-structured-outputs-v4.rb

require 'json'
require 'dry-schema'
require 'openai'
require 'ostruct'

module StructuredOutputs
  # Schema class for defining JSON schemas
  class Schema
    MAX_OBJECT_PROPERTIES = 100
    MAX_NESTING_DEPTH = 5

    def initialize(name = nil, &block)
      # Use the provided name or derive from class name
      @name = name || self.class.name.split('::').last.downcase
      # Initialize the base schema structure
      @schema = {
        type: 'object',
        properties: {},
        required: [],
        additionalProperties: false,
        strict: true
      }
      @definitions = {}
      # Execute the provided block to define the schema
      instance_eval(&block) if block_given?
      validate_schema
    end

    # Convert the schema to a hash format
    def to_hash
      {
          name: @name,
          description: "Schema for the structured response",
          schema: @schema.merge({ '$defs' => @definitions })
      }
    end
    
    private

    # Define a string property
    def string(name, enum: nil, description: nil)
        add_property(name, { type: 'string', enum: enum, description: description }.compact)
    end

    # Define a number property
    def number(name)
      add_property(name, { type: 'number' })
    end

    # Define a boolean property
    def boolean(name)
      add_property(name, { type: 'boolean' })
    end

    # Define an object property
    def object(name, &block)
      properties = {}
      required = []
      Schema.new.tap do |s|
        s.instance_eval(&block)
        properties = s.instance_variable_get(:@schema)[:properties]
        required = s.instance_variable_get(:@schema)[:required]
      end
      add_property(name, { type: 'object', properties: properties, required: required, additionalProperties: false })
    end

    # Define an array property
    def array(name, items:)
      add_property(name, { type: 'array', items: items })
    end

    # Define an anyOf property
    def any_of(name, schemas)
      add_property(name, { anyOf: schemas })
    end

    # Define a reusable schema component
    def define(name, &block)
      @definitions[name] = Schema.new(&block).instance_variable_get(:@schema)
    end

    # Reference a defined schema component
    def ref(name)
      { '$ref' => "#/$defs/#{name}" }
    end

    # Add a property to the schema
    def add_property(name, definition)
      @schema[:properties][name] = definition
      @schema[:required] << name
    end

    # Validate the schema against defined limits
    def validate_schema
      properties_count = count_properties(@schema)
      raise 'Exceeded maximum number of object properties' if properties_count > MAX_OBJECT_PROPERTIES

      max_depth = calculate_max_depth(@schema)
      raise 'Exceeded maximum nesting depth' if max_depth > MAX_NESTING_DEPTH
    end

    # Count the total number of properties in the schema
    def count_properties(schema)
      return 0 unless schema.is_a?(Hash) && schema[:properties]
      count = schema[:properties].size
      schema[:properties].each_value do |prop|
        count += count_properties(prop)
      end
      count
    end

    # Calculate the maximum nesting depth of the schema
    def calculate_max_depth(schema, current_depth = 1)
      return current_depth unless schema.is_a?(Hash) && schema[:properties]
      max_child_depth = schema[:properties].values.map do |prop|
        calculate_max_depth(prop, current_depth + 1)
      end.max
      [current_depth, max_child_depth].max
    end
  end

  # Client class for interacting with OpenAI API
  class OpenAIClient
    def initialize
      OpenAI.configure do |config|
        config.access_token = ENV.fetch("OPENAI_ACCESS_TOKEN")
        config.log_errors = true
      end
      @client = OpenAI::Client.new
    end

    # Send a request to OpenAI API and parse the response
    def parse(model:, messages:, response_format:)
      response = @client.chat(
        parameters: {
          model: model,
          messages: messages,
          response_format: { 
            type: "json_schema",
            json_schema: response_format.to_hash
          }
        }
      )

      content = JSON.parse(response['choices'][0]['message']['content'])
      
      if response['choices'][0]['message']['refusal']
        OpenStruct.new(refusal: response['choices'][0]['message']['refusal'], parsed: nil)
      else
        OpenStruct.new(refusal: nil, parsed: content)
      end
    end
  end
end

# Example usage: Define a schema for math reasoning
class MathReasoning < StructuredOutputs::Schema
  def initialize
    super do
      define :step do
        string :explanation
        string :output
      end
      array :steps, items: ref(:step)
      string :final_answer
    end
  end
end

begin
  # Create an OpenAI client
  client = StructuredOutputs::OpenAIClient.new
  # Create an instance of the MathReasoning schema
  schema = MathReasoning.new
  
  # Send a request to OpenAI API
  result = client.parse(
    model: "gpt-4o-2024-08-06",
    messages: [
      { role: "system", content: "You are a helpful math tutor. Guide the user through the solution step by step." },
      { role: "user", content: "how can I solve 8x + 7 = -23" }
    ],
    response_format: schema
  )
  
  # Handle the response
  if result.refusal
    puts "The model refused to respond: #{result.refusal}"
     
  else
    puts JSON.pretty_generate(result.parsed)
     
  end

rescue => e
  puts "Error: #{e}"
end

Thanks for sharing this!

Just to let you know that you are missing:

Descriptions — e.g.:

def string(name, enum: nil, description: nil)
    add_property(name, { type: 'string', enum: enum, description: description }.compact)
end

Definitions in the .to_hash method:

def to_hash
    {
        name: @name,
        description: "Schema for the structured response",
        schema: @schema.merge({ '$defs' => @definitions })
    }
end

@danielfriis thanks! Updated.