DelegateCached

Overview

delegate_cached allows you to cache delegated attributes on the delegating model and provides options to update the cached values when changed on the delegated-to model.

Installation

Add this line to your application's Gemfile:

gem 'delegate_cached'

And then execute:

$ bundle

Or install it yourself as:

$ gem install delegate_cached

Usage

We'll be caching the delegated attribute value, so your delegating ActiveRecord model will need a column to store the value. The column name will need to match the delegated attribute, or if using the prefix: true option, match the delegated attribute preceded by the to: option and _. For example, as below, the column names required would be hiker_name for the first delegate_cached definition, and name for the second. Create and run a migration for your new column/s unless they already exist.

class ThruHike < ApplicationRecord
  belongs_to :hiker, inverse_of: :thru_hikes
  belongs_to :trail, inverse_of: :thru_hikes

  delegate_cached :name, to: :hiker, prefix: true # 'hiker_name' column required on thru_hikes table
  delegate_cached :name, to: :trail               # 'name' column required on thru_hikes tables
end

Now, add your delegate_cached definition as in the example above. Note - you may only use delegate_cached on belongs_to and has_one associations.

Finally, use your models as you typically would with delegate When an instance of the delegated-to model is saved, a callback will update your delegate_cached value.

Options

update_when_nil: true False by default. When set to true and the referenced attribute is called, if the existing cached value is nil, it will attempt to update the attribute value with the delegated value.

skip_callback: true False by default. When set to true, the after_save callback on the delegated-to model will not set.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/cselmer/delegate_cached. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests.