Creating nested hash from nested active record results

rubyonrails-talk
1

Hello,   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:

[code] results_to_hash = Hash[ found_categories.map{ |c| [c.id, c.title]}] [/code]

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:

[code] results_to_hash = Hash[ found_categories.map{ |c| [c.id, c.title, c.categories]}] [/code]

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?

Thanks, Eric

2

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.

3

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: https://github.com/flyerhzm/bullet

4

Just an FIY - this was my solution:

[code]    def self.active_record_to_array_of_hashes(array_collection, sub_collection_names=)      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|          if(obj.class.reflections.keys.include?(name))            tmp_hash[name] = ActiveSupport::JSON.decode(obj.send(name).to_json)          end        end        hashed_collection << tmp_hash      end      return hashed_collection    end [/code]