Preview Ruby 4.1 is a preview. It can change before the final release. Switch to Ruby 4.0 →

class method

JSON::Coder.new

JSON::Coder.new(**options, &block)

ext/json/lib/json/common.rb View on GitHub ↗

# File tmp/rubies/ruby-4.1.0-preview1/ext/json/lib/json/common.rb, line 833
def initialize(object_class: nil, array_class: nil, on_load: nil, strict: true, **options, &as_json)
  raise ArgumentError, "JSON::Coder requires strict mode" unless strict

  if object_class || array_class
    on_load = ParserOptions.on_load(on_load, object_class, array_class)
  end
  parser_options = options.slice(*PARSER_OPTIONS)
  parser_options[:on_load] = on_load if on_load
  @parser_config = Ext::Parser::Config.new(parser_options).freeze

  generator_options = options.reject { |k, _| EXCLUDED_GENERATOR_OPTIONS.include?(k) }
  @state = State.new(
    **generator_options,
    strict: true,
    as_json: as_json || generator_options[:as_json],
  ).freeze
end

Keyword arguments options, if given, are options for both parsing and generating. See Parsing Options, and Generating Options.

For generation, the strict: true option is always set. When a Ruby object with no native JSON counterpart is encountered, the block provided to the initialize method is invoked, and must return a Ruby object that has a native JSON counterpart:

Example

module MyApp
  API_JSON_CODER = JSON::Coder.new do |object|
    case object
    when Time
      object.iso8601(3)
    else
      object # Unknown type, will raise
    end
  end
end

puts MyApp::API_JSON_CODER.dump(Time.now.utc) # => "2025-01-21T08:41:44.286Z"

The conversion callback can also be passed as as_json:. If both are given, the block takes precedence. Passing false or nil for strict: raises ArgumentError.