Friendly URLs in Rails

friendly_urls.markdown

Friendly URLs

By default, Rails applications build URLs based on the primary key -- the id column from the database. Imagine we have a Person model and associated controller. We have a person record for Bob Martin that has id number 6. The URL for his show page would be:

/people/6

But, for aesthetic or SEO purposes, we want Bob's name in the URL. The last segment, the 6 here, is called the "slug". Let's look at a few ways to implement better slugs.

Simple Approach

The simplest approach is to override the to_param method in the Person model. Whenever we call a route helper like this:

person_path(@person)

Rails will call to_param to convert the object to a slug for the URL. If your model does not define this method then it will use the implementation in ActiveRecord::Base which just returns the id.

For this method to succeed, it's critical that all links use the ActiveRecord object rather than calling id. Don't ever do this:

person_path(@person.id) # Bad!

Instead, always pass the object:

person_path(@person)

Slug Generation

Instead, in the model, we can override to_param to include a parameterized version of the person's name:

class Person < ActiveRecord::Base
  def to_param
    [id, name.parameterize].join("-")
  end
end

For our user Bob Martin with id number 6, this will generate a slug 6-bob_martin. The full URL would be:

/people/6-bob-martin

The parameterize method from ActiveSupport will deal with converting any characters that aren't valid for a URL.

Object Lookup

What do we need to change about our finders? Nothing! When we call Person.find(x), the parameter x is converted to an integer to perform the SQL lookup. Check out how to_i deals with strings which have a mix of letters and numbers:

> "1".to_i
# => 1 
> "1-with-words".to_i
# => 1 
> "1-2345".to_i
# => 1 
> "6-bob-martin".to_i
# => 6 

The to_i method will stop interpreting the string as soon as it hits a non-digit. Since our implementation of to_param always has the id at the front followed by a hyphen, it will always do lookups based on just the id and discard the rest of the slug.

Benefits

We've added content to the slug which will improve SEO and make our URLs more readable.