Undocumented :inverse_of option for ActiveRecord associations

Note: Instead of using the method in this card, you probably want to use ActiveType's nested attributes which is a much more refined way of doing this.

The attach...

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...

Finish the remainder of the ActiveModel todo list (observers, callbacks, validations, scoping, and serialization) in addition to associations. Also wire up ActiveModel up to ActiveRecord and ActiveResource.

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...

Let's say you need to revert a migration that happened a while back. You'd create a new migration that removes what was added back then in the up path, while its down path restores the old functionality.

While you could just copy&paste the `d...

For Rails models where only one of multiple attributes may be filled out at the same time, there is no built-in validation.

I've seen different solutions in the wild, each with different downsides:

• Private method referenced via validate: wor...

Let's say we have posts with an attribute title that is mandatory.

Our example feature request is to tag these posts with a limited number of tags. The following chapters explain different approaches in Rails, how you can assign such a...

When your Rails controller calls render, you can pass a :status option for the HTTP status code:

render 'results', status: 400

All important status codes also have a symbol alias, which makes your code easier to read:

render 're...

Code example for implementing Cross-Origin Resource Sharing (CORS) in Rails.

Let's say you have a form that you render a few times but you would like to customize your submit section each time. You can achieve this by rendering your form partial as layout and passing in a block. Your template or partial then serves as the ...