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Common::Models

Common::Models provides base classes and mixins for building serializable, sortable, filterable, and Redis-backed data models across vets-api.

Purpose

To establish consistent conventions for non-ActiveRecord models: how they declare attributes, how collections of them are paginated and filtered, and how short-lived objects are stored and retrieved from Redis.

Classes

Common::Base

The foundation for non-ActiveRecord model objects. Includes ActiveModel::Serialization, Virtus.model, and Comparable. Subclasses declare typed attributes via Virtus and can mark them as sortable or filterable for use with Common::Collection.

class Prescription < Common::Base
  attribute :prescription_id, Integer, sortable: { order: 'ASC', default: true }
  attribute :status, String, filterable: %w[eq not_eq]
  attribute :dispensed_date, Common::UTCTime, sortable: { order: 'DESC' }
end

Tracks attribute changes (changed?, changed, changes) relative to the values at initialization.

Common::Collection

A wrapper around an array of model objects that adds filtering, sorting, and pagination. Accepts a cache_key to transparently back the collection with Redis (1-hour TTL by default).

collection = Common::Collection.fetch(Prescription, cache_key: cache_key, ttl: 3600) do
  { data: prescriptions, metadata: {}, errors: {} }
end

collection.find_by(status: { eq: 'active' })
          .sort('-dispensed_date')
          .paginate(page: 1, per_page: 10)

Filtering operators: eq, not_eq, lteq, gteq, match. Only attributes declared as filterable on the model class can be used. Sort fields must be declared as sortable.

Common::RedisStore

An ActiveModel-compatible base class for objects that are persisted to Redis rather than a relational database. Subclasses configure their namespace, TTL, and key attribute using class-level declarations.

class MySession < Common::RedisStore
  redis_store 'my_session'
  redis_ttl 3600
  redis_key :token

  attribute :token, String
  attribute :user_id, Integer
end

session = MySession.find(token)
session = MySession.find_or_build(token)
session.save
session.destroy

Requires redis_store and redis_key to be set. Objects are serialized to JSON via Oj. Invalid objects are automatically removed from Redis on retrieval.

Common::Resource

A thin subclass of Dry::Struct for immutable, typed value objects. Prefer this over Common::Base when the object should be strictly typed and immutable by design.

class AddressInfo < Common::Resource
  attribute :street, Types::Strict::String
  attribute :city, Types::Strict::String
end

Supporting Classes

Common::CacheAside — a concern for Common::RedisStore subclasses that implements the cache-aside pattern. Wraps a block, checks the cache first, and stores the result if the response reports itself as cacheable (response.cache?).

Common::UTCTime — a Virtus attribute type that coerces all time values to UTC. Use it in Common::Base subclasses to ensure consistent time handling.

Comparable::Ascending / Comparable::Descending — internal wrappers used by Common::Collection#sort to support multi-field sorting with mixed directions.