Creating nested hash from nested active record results

  I'm trying to find a very abstract and "one size fits all" for
converting nested active record results to nested hashes. It's easy,
to do one level deep as such:

results_to_hash = Hash[{ |c| [, c.title]}]

But, when I try to add another collection to the mix, it completely
borks and the results_to_hash only returns an empty hash IE:

results_to_hash = Hash[{ |c| [, c.title,

Ultimately, I'd like it to be smart enough to detect if a model object
contains a collection (IE: object.class.reflect_on_all_associations),
and automatically convert those to hashes.

Any ideas?


Would this work?

MyModel.last.serializable_hash methods: MyModel.reflections.keys

Or is that too much?

Look at the options that you can pass into serializable_hash.

However, if you are doing this for json/etc. serialization in the controller, check out ActiveModel::Serializers.

One note about this: this can hit n+1 queries pretty hard. Unless you put include: in your associations (which I wouldn’t not recommend unless it makes sense, and it probably doesn’t) you have to know at query time what to include (or use joins), and what I just posted would make that difficult.

If you do use ActiveModel::Serializers instead and have big serialized objects, look at yodo to help you identify the value for include: in your queries to avoid n+1:

You could also look at bullet in that regard:

Just an FIY - this was my solution:

   def self.active_record_to_array_of_hashes(array_collection,
     hashed_collection = []
     array_collection.each do |obj|
       tmp_hash = ActiveSupport::JSON.decode(obj.to_json)

       #### hashify specified model association
       sub_collection_names.each do |name|
           tmp_hash[name] =
       hashed_collection << tmp_hash
     return hashed_collection