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Creating nested hash from nested active record results

Posted on 2013-05-22
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Last Modified: 2014-10-27
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:
 
results_to_hash = Hash[ found_categories.map{ |c| [c.id, c.title]}]

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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[ found_categories.map{ |c| [c.id, c.title, c.categories]}]

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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
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Question by:clemcrock
2 Comments
 
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Expert Comment

by:fridom
ID: 39265035
It might be that you need a deep copy of the collection. AFAIK are assignments to array just "shallow" that means if you have a collection [1,2,3]

and you add it to a hash
ht.Add(key => #someKey, value => #collection)
and you change a collection thereafter the  hash table collection gets influenced also.

So in this case you probably want to use clone

If not please provide code that we can use.

Regards
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Accepted Solution

by:
clemcrock earned 0 total points
ID: 39757672
Just an FIY - this was my solution:

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

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