Using sets for many-to-many relationships

Find conditions for scopes can be given either as an array (:conditions => ['state = ?', 'draft']) or a hash (:conditions => { 'state' => 'draft' }). The later is nicer to read, but has horrible security implications in some versions of Ru...

When you render a nested form for a Movie which has_many :actors, you want to render the right number of blank Actor forms. The right number means:

• A minimum number of blank forms so the user can add more Actors to an existing Movie, ...

While it might seem trivial to implement an invoice that sums up items and shows net, gross and vat totals, it actually involves a lot of rules and caveats. It is very easy to create invoices where numbers don't add up and a few cents are missing....

When you have two models in a has_many, has_one or belongs_to association, the :inverse_of option in Rails tells ActiveRecord that they're two sides of the same association.

Example with a has_many / belongs_to association:

c...

Here are some popular mistakes when using nested forms:

• You are using fields_for instead of form.fields_for.
• You forgot to use accepts_nested_attributes in the containing model. Rails won't complain, but nothing will work. In particular...

Tod is a gem for working with daytimes.

Another additional gem?

Thus SQL has a time datatype for storing time of day in the format hh:mm:ss, neither Ruby nor Rails themselves offer an elegant way to deal with day times.

Time and `Dat...

Note: Consider not doing this. Use form models or vanilla methods instead.

The :conditions option for Rails associations cannot take a lambda. This makes it hard to define conditions that must be evaluated at runtime, e.g. i...

While upgrading CarrierWave from version 0.11.x to 3.x, we encountered some very nasty fails. Below are the basic changes you need to perform and some behavior you may eventually run into when upgrading your application. This aims to save you some...

A flaky test is a test that is often green, but sometimes red. It may only fail on some PCs, or only when the entire test suite is run.

There are many causes for flaky...