How to cache an array using Active Model Serializers (0.8)? - ruby-on-rails

Question

On an individual Active Model Serializer you can specify the cache key within your serializer, i.e.
Caching a single object using AMS
class OrgSerializer < ActiveModel::Serializer
cached
delegate :cache_key, to: :object
end
Array caching
I need to deliver an array of these objects:
array_json = ActiveModel::ArraySerializer.new(Org.all.limit(50)).to_json
Rather than do 50 cache hits to construct the array I want to do a single cache hit and expire it when any of the array elements expires.
How to cache the array (and construct the key)?
I therefore want a cache key for the array that is made up of the individual object IDs and their last-updated at date like this:
def cache_key_for_collection collection
keys = collection.collect{|element| "#{element.id}#{element.updated_at}" }
keys.join ""
end
How can you do this with AMS (0.8)?
Does the AMS array serializer allow for this or is it something that needs to just be done manually? Is there a way to declare that you want caching and how the key should be constructed?
If it doesn't do it then what would be the neatest way to manually construct the cache/key?

Answer 1

It works very similarly to standard Serializers. You will create a custom ArraySerializer that looks something like this:
class BaseArraySerializer < ActiveModel::ArraySerializer
cached
def cache_key
keys = object.map{|obj| "#{obj.id}-#{obj.updated_at.to_s(:number)}" }
keys.join "/"
end
end
The one thing to note is that you are still doing object.map instead of objects, but this is purely how AMS 0.8.0 is implemented.
Then to deliver the json the only change you would have to make is:
array_json = ActiveModel::ArraySerializer.new(Org.all.limit(50)).to_json