Module: Commutator::Collection::CachedLookup

Defined in:

lib/commutator/collection/cached_lookup.rb

Overview

Implemention of a per-collection cache to avoid repeating expensive lookups. E.g. if several items in the collection refer to the same User object, the following pattern would ensure the User is only looked up once:

# (inside your model)
CachedUserLookup = Proc.new do
  Commutator::Collection::CachedLookup.new(:user, :user_id) do |user_id|
    User.find(user_id)
  end
end

modify_collection_items_with CachedUserLookup, factory: true

Note: The cache itself is not accessible since it’s hidden by the closure

scope. Additionally, this returns the same instance of the object for
every matching lookup - so be mindful when modifying that object.

Class Method Summary

• .new(attr_name, item_key, &block) ⇒ Object

Class Method Details

.new(attr_name, item_key, &block) ⇒ Object

# File 'lib/commutator/collection/cached_lookup.rb', line 21

def self.new(attr_name, item_key, &block)
  cache = Hash.new do |h, k|
    h[k] = block.call(k)
  end

  Proc.new do |item|
    item.define_singleton_method(attr_name) do
      cache[item.send(item_key)]
    end
  end
end