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Polymorphic Association (revised)
A polymorphic association allows a model to belong_to different types of other models. Here I show how to make a single comment model belong to articles, photos, and events.
(11 minutes)
A Tour of State Machines
Here I show how three popular state machine gems can be used to clean up a list of boolean/datetime fields. I also show a custom solution which keeps track of the history of events.
(12 minutes)
STI and Polymorphic Associations
Single Table Inheritance (STI) can help organize branching logic into separate classes, but a polymorphic association may be a better fit if there are unique database columns.
(14 minutes)
Active Record Reputation System
If you need to calculate an average user's rating or sum up a number of votes, consider using the activerecord-reputation-system gem. Here I will cover the basics and also briefly present a from-scratch solution.
(10 minutes)
Migrating to PostgreSQL
Postgres is a feature-packed relational database that every Rails developer should consider using. Here you will learn how to install it, add it to a new application, and transition from an existing SQLite app using the "taps" gem.
(8 minutes)
Full-Text Search in PostgreSQL
Postgres offers full-text searching right out of the box. This episode shows how to write queries from scratch, apply tools like Texticle and pg_search, and optimize performance through indexes.
(16 minutes)
Virtual Attributes (revised)
Virtual attributes are a clean way to add form fields that do not map directly to the database. Here I show how to handle validations, associations, and more.
(11 minutes)
Hacking with Arel
Here I show a variety of ways to rewrite a long SQL query using only Active Record and Arel. This includes generating scopes dynamically, adding an "or" operator, and adding a powerful "match" method.
(15 minutes)
Squeel
Squeel provides a comprehensive DSL for writing SQL queries in Ruby. It is built upon Arel giving you access to many of its powerful features.
(9 minutes)
HABTM Checkboxes (revised)
A many-to-many association can be edited through check boxes in a form. Here I show how to do this with a has_many through association complete with clickable labels.
(6 minutes)