ActiveRecord serialize loader for ActiveModel::Serializers

json_array.rb

class JSONArray

  attr_accessor :object_class, :serializer_class

  def initialize(object_class, serializer_class = nil)
    @object_class = object_class
    @serializer_class = serializer_class || object_class.new.active_model_serializer
  end

  def dump(arr)
    return if arr.nil?

    unless arr.is_a?(::Array)
      raise ::ActiveRecord::SerializationTypeMismatch, "Attribute was supposed to be an Array, but was a #{arr.class}. -- #{arr.inspect}"
    end

    arr.each do |obj|
      unless obj.is_a?(object_class)
        raise ::ActiveRecord::SerializationTypeMismatch, "Attribute was supposed to be a #{object_class}, but was a #{obj.class}. -- #{obj.inspect}"
      end
    end

    ::ActiveModel::ArraySerializer.new(arr, each_serializer: serializer_class).to_json
  end

  def load(json)
    return [] if json.nil?
    arr = ::JSON.parse(json)

    unless arr.is_a?(::Array)
      raise ::ActiveRecord::SerializationTypeMismatch, "Attribute was supposed to be an Array, but was a #{arr.class}. -- #{arr.inspect}"
    end

    arr.collect { |obj|
      if obj.is_a?(object_class)
        obj
      else
        object_class.new(obj)
      end
    }
  end

end

json_model.rb

class JSONModel

  attr_accessor :object_class, :serializer_class, :return_nil

  def initialize(object_class, serializer_class: nil, return_nil: true)
    @object_class = object_class
    @serializer_class = serializer_class || object_class.new.active_model_serializer
    @return_nil = return_nil
  end

  def dump(obj)
    return if obj.nil?

    unless obj.is_a?(object_class)
      raise ::ActiveRecord::SerializationTypeMismatch, "Attribute was supposed to be a #{object_class}, but was a #{obj.class}. -- #{obj.inspect}"
    end

    serializer_class.new(obj).to_json
  end

  def load(json)
    return nil if return_nil && json.nil?
    return object_class.new if object_class != Object && json.nil?
    return json unless json.is_a?(String)

    data = ::JSON.load(json)

    data.is_a?(object_class) ? data : object_class.new(data)
  end

end

topic.rb

# Example of usage. Topic::Options and Topic::Step are Virtus objects with coercion 
# and with included ActiveModel::SerializerSupport
class Topic < ActiveRecord::Base
  serialize :options, JSONModel.new(Topic::Options)
  serialize :steps, JSONArray.new(Topic::Step)
end