Serializable Ruby Hash from an array of Rails objects that you need the hash key as object id and extra props

serializable_hash_from_rails_objects_merge.rb

def methodToReturnHashMap
  Hash[ self.some_method_that_returns_array_of_rails_objects.collect { |obj|
    [obj.id , obj.attributes.merge({
      extra: 'value',
      another_extra: 'value'
    })]
  }]
end


##
## Then can be used on a model for json exposed to frontend.
## {
##   json: <%= mymodel.methodToReturnHashMap.to_json %>
## }