Nested and recursive JSON input handling - ruby-on-rails

Question

I am building a REST API using rails and I have a few controllers that accept nested and recursive JSON, for example, when doing a PUT on /taxonomies/:id.json you can pass something like:
{
"names":[
"brands",
"secondary_brands"
],
"taxonomy_data":{
"some":"data"
},
"terms":[
{
"slug":"apple",
"data":{
"value":"Apple California"
},
"overridable_data":{
"weight":0.5
},
"term_data":{
"description":{
"en":"Apple makes the iPhone"
}
}
},
{
"slug":"microsoft",
"data":{
"value":"Microsoft Inc"
},
"overridable_data":{
"weight":0.5
},
"term_data":{
"description":{
"en":"Microsoft makes windows"
}
},
"children":[
{
"data":{
"value":"Xbox"
},
"overridable_data":{
"weight":0.5
},
"term_data":{
"description":{
"en":"Xbox one is bad"
}
}
}
]
},
{
"slug":"hp",
"data":{
"value":"HP Inc"
},
"overridable_data":{
"weight":0.5
},
"term_data":{
"description":{
"en":"HP makes atomic clocks"
}
}
}
]
}
Right now, I put the following code in my model:
class Taxonomy < ActiveRecord::Base
has_many :terms,
-> {order(:id)}
def update_terms(params)
existing_term_ids = terms.map &:id
create_term = lambda do |term_params, parent=nil|
t = terms.find_by(:id => term_params[:id]) if term_params[:id]
t ||= terms.build
t.attributes = term_params.slice(:slug, :data, :overridable_data, :term_data)
t.parent = parent
t.save
existing_term_ids.delete(t.id)
if term_params.has_key?(:children)
term_params[:children].each do |child_params|
create_term.call(child_params, t)
end
end
end
params.each do |term_params|
create_term.call(term_params)
end
terms.where(:id => existing_term_ids).destroy_all
save
end
end
This version (rapidly written to test rails 4) uses slice to filter parameters because attr_accessible is gone.
This makes me wonder if this kind of code should be in the model or the controller.

Answer 1

Read this acticle: http://blog.codeclimate.com/blog/2012/10/17/7-ways-to-decompose-fat-activerecord-models/
My opinion, you should do the service in this case, something like this:
# app/services/recursive_update.rb
class RecursiveUpdate
def initalize(source)
#source = source
end
def update(params)
# your code here
end
def create_term(term_params, parent=nil)
#....
end
def permitted_params
#....
end
def save
#source.save
end
end
in the controller:
updater = RecurciveUpdate.new #model
updater.update params
update.save