thing_service.rb

# frozen_string_literal: true

class Things::Something
  Result = Data.define(:thing, :errors) do
    def initialize(thing: nil, errors: [])
      super
    end

    def successful?
      errors.empty?
    end
  end

  def self.call(params, scope = ThingModel)
    new(params, scope).call
  end

  def call
    something = find_or_process_things

    if something.successful?
      Result.new(thing: something)
    else
      Result.new(errors: something.errors, thing: something)
    end
  end

  def initialize(params, scope)
    @params = params
    @scope = scope
  end
  private_class_method :new

  private

  def find_or_process_things
    @scope.where(...)
  end
end

# Usage
result = Things::Something.call(params) # => Things::Something::Result
result.successful? # => true
result.errors # => []
result.thing # => <ThingRecord...