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Seven Useful ActiveModel Validators

Custom ActiveModel::Validators are an easy way to validate individual attributes on your Rails models. All that's required is a Ruby class that inherits from ActiveModel::EachValidator and implements a validate_each method that takes three arguments: record, attribute, and value. I have written a few lately, so I pinged the rest of the amazingly talented Viget developers for some contributions. Here's what we came up with.

First-Class Failure

As a developer, nothing makes me more nervous than third-party dependencies and things that can fail in unpredictable ways1. More often than not, these two go hand-in-hand, taking our elegant, robust applications and dragging them down to the lowest common denominator of the services they depend upon. A recent internal project called for slurping in and then reporting against data from Harvest, our time tracking service of choice and a fickle beast on its very best days.

I knew that both components (/(im|re)porting/) were prone to failure. How to handle that failure in a graceful way, so that our users see something more meaningful than a 500 page, and our developers have a fighting chance at tracking and fixing the problem? Here’s the approach we took.

Identifying Foreign Key Dependencies from ActiveRecord::Base Classes

Ever find yourself in a situation where you were given an ActiveRecord model and you wanted to figure out all the models it had a foreign key dependency (belongs_to association) with? Well, I had to do just that in some recent sprig-reap work. Given the class for a model, I needed to find all the class names for its belongs_to associations.

In order to figure this out, there were a few steps I needed to take..

Identify the Foreign Keys / belongs_to Associations

ActiveRecord::Base-inherited classes (models) provide a nice interface for inspecting associations -- the reflect_on_all_associations method. In my case, I was looking specifically for belongs_to associations. I was in luck! The method takes an optional argument for the kind of association. Here's an example:

# => array of ActiveRecord::Reflection::AssociationReflection objects

Once I had a list of all the belongs_to associations, I needed to then figure out what the corresponding class names were.

Identify the Class Name from the Associations

When dealing with ActiveRecord::Reflection::AssociationReflection objects, there are two places where class names can be found. These class names are downcased symbols of the actual class. Here are examples of how to grab a class name from both a normal belongs_to association and one with an explicit class_name.

Normal belongs_to:

class Post < ActiveRecord::Base
  belongs_to :user

association = Post.reflect_on_all_associations(:belongs_to).first
# => ActiveRecord::Reflection::AssociationReflection instance

name =
# => :user

With an explicit class_name:

class Post < ActiveRecord::Base
  belongs_to :creator, class_name: 'User'

association = Post.reflect_on_all_associations(:belongs_to).first
# => ActiveRecord::Reflection::AssociationReflection instance

name = association.options[:class_name]
# => 'User'

Getting the actual class:

ActiveRecord associations have a build in klass method that will return the actual class based on the appropriate class name:

# => User

Building a Javascript Game with EaselJS and Box2D: Part 1

Ever since we made Say Viget! we've had a bunch of people asking us to explain exactly how we did it. This post is a first go at that explanation -- and a long one at that. Because so much goes into making a game, this is Part 1 of a multi-part series on how to build a 2D Javascript game, explaining some theory, best practices, and highlighting some helpful libraries.

If you're reading this then you probably know the basics: we use Javascript to add things to the context of a canvas while moving those things around through a loop (which is hopefully firing at ~60fps). But how do you achieve collisions, gravity, and general gameplay-smoothness? That's what this post will cover.

Getting started with inline SVG

This May, Viget worked with Dick's Sporting Goods to launch Women's Fitness, an interactive look at women’s fitness apparel and accessories. One of it's most interesting features is the grid of hexagonal product tiles shown in each scene. To draw the hexagons, I chose to use SVG polygon elements.

I've had experience using SVG files as image sources and in icon fonts, but this work was my first opportunity to really dig into it's most powerful use case, inline in HTML. Inline SVG simply refers to SVG markup that is included in the markup for a webpage.


<div><svg><!-- WHERE THE MAGIC HAPPENS. --></svg></div>


Based on this experience, here are a few simple things I learned about SVG.