caching.md

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Caching

To cache a serializer, call cache and pass its options. The options are the same options of ActiveSupport::Cache::Store, plus a key option that will be the prefix of the object cache on a pattern "#{key}/#{object.id}-#{object.updated_at}".

The cache support is optimized to use the cached object in multiple request. An object cached on a show request will be reused at the index. If there is a relationship with another cached serializer it will also be created and reused automatically.

[NOTE] Every object is individually cached.

[NOTE] The cache is automatically expired after an object is updated, but it's not deleted.

cache(options = nil) # options: ```{key, expires_in, compress, force, race_condition_ttl}```

Take the example bellow:

class PostSerializer < ActiveModel::Serializer
  cache key: 'post', expires_in: 3.hours
  attributes :title, :body

  has_many :comments
end

On this example every Post object will be cached with the key "post/#{post.id}-#{post.updated_at}". You can use this key to expire it as you want, but in this case it will be automatically expired after 3 hours.

Fragment Caching

If there is some API endpoint that shouldn't be fully cached, you can still optimise it, using Fragment Cache on the attributes and relationships that you want to cache.

You can define the attribute by using only or except option on cache method.

[NOTE] Cache serializers will be used at their relationships

Example:

class PostSerializer < ActiveModel::Serializer
  cache key: 'post', expires_in: 3.hours, only: [:title]
  attributes :title, :body

  has_many :comments
end