Schnecke

A very simple gem to enable ActiveRecord models to have slugs.

Installation

Add this line to your application's Gemfile:

gem 'schnecke'

And then execute:

$ bundle

Or install it yourself as:

$ gem install schnecke

Usage

Given a class SomeObject which has the attribute name and has a slug column defined, we can do the following:

class SomeObject
  include Schnecke
  slug :name
end

This will take the value in name and automatically set the slug based on it. If the slug needs to be based on multiple attributes of a model, simply pass in the array of attributes as follows:

class SomeObject
  include Schnecke
  slug [:first_name, :last_name]
end

Under the hood, this library adds a before_validate callback that automatically runs a method called assign_slug. You are welcome to call this method explicity if you so desire.

obj = SomeObject.new(name: 'Hello World!')
obj.assign_slug

It is important to note that if the attribute used to hold the slug (slug by default, see next section) already contains a value, the slug assignment WILL NOT HAPPEN. This means, if you manually assign the slug by explicitly setting the slug value yourself, it will not be modified. If you would like the slug to be overwrriten you can explicitly call the reassign_slug method.

obj = SomeObject.new(name: 'Hello World!', slug: 'hi')

# This will do nothing as the slug was already set
obj.assign_slug

# This will cause the slug to be assigned
obj.reassign_slug

Using a method to define a slug source

There are times when the source of the slug needs to be set based on some other values (e.g. a parent object, random number, etc). In this case, simply define a method that is to be used to set the soure of the slug. This method can be public, protected, or private.

class SomeObject
  include Schnecke
  slug :parent_slug

  belongs_to :parent_object

  protected

  def parent_slug
    parent_object.slug
  end
end

Just like if one is using a plain old attributes, one can mix and match methods and attributes if the slug is to be derived from multiple sources

class SomeObject
  include Schnecke
  slug [:name, :parent_slug]

  belongs_to :parent_object

  protected

  def parent_slug
    parent_object.slug
  end
end

And this will take the :name attribute and the result from parent_slug and create a slug from the two things combined.

Slug column

By default it is assumed that the generated slug will be assigned to the slug attribute of the model. If one needs to place the slug in a different columm, this can be done by defining the column attribute:

class SomeObject
  include Schnecke
  slug :name, column: :some_other_column
end

The above will place the generated slug in some_other_column.

Setting the maximum length of a slug

By default the maxium length of a slug is 32 characters NOT INCLUDING any potential sequence numbers added to make it unique (see the "Handling non-unique slugs" section). You can either change the maximum or remove it entirely as follows

class SomeObject
  include Schnecke
  slug :name, limit_length: 15
end

class SomeObject
  include Schnecke
  slug :name, limit_length: false
end

Slug Uniquness

By default slugs are unique to the object that defines the slug. For example if we have the 2 objects, SomeObject and SomeOtherObject as defined as below, then the slugs will be unique for all slugs for all type SomeObject objcets and all type SomeOtherObject objects.

class SomeObject
  include Schnecke
  slug :name
end

class SomeOtherObject
  include Schnecke
  slug :name
end

This means that the slug foo can exists 2 times; once for any object of type SomeObject and once for any object of type SomeOtherObject. Currently there is no way to create globally unique slugs. If this is something that is required, then something like friendly_id might be more appropriate for your use case.

Handling non-unique slugs

If a duplicate slug is to be created, a number is automatically appended to the end of the slug. For example, if there is a slug foo, the second one would become foo-2, the third foo-3, and so forth.

It is important to note that the maximum length of a slug does not include the addition of the sequence identifier at the end. By default the maximum length of a slug is 32 characters, but if a sequence number is added, it will be 34 characters when we append the -2, -3, etc. This was done on purpose so that the base slug always remains constant and does not get truncated.

Defining a custom uniqueness scope

There are times when we want slugs not be unique for all objects of type SomeObject, but rather for a smaller scope. For example, let's say we have a system with multiple Accounts, each containing Records. If we want the slug for the Record to be unique only within the scope of an account we can do by providing the uniqueness scope when setting up the slug.

class Record
  include Schnecke
  slug :name, uniqueness: { scope: :account }

  belongs_to :account
end

When we do this, this will let us have the same slug 'foo' for multiple record objects as long as they belong todifferent accounts. Note, we can also pass an array so that we can define the scope even more narrowly. For example:

class Tag
  include Schnecke
  slug :name, uniqueness: { scope: [:account, :record] }

  belongs_to :account
  belongs_to :record
end

Callbacks

Two callbacks, before_assign_slug and after_assign_slug, are provided so that you can run arbitrary code before and after the slug assignment process. Both of these callbacks will always run regardless of whether or not a slug is to be assigned. The only time after_assign_slug is not run is if there is an exception raised during the assignment process.

Note, since reassign_slug is just a forced assignment of a slug, both callbacks will run as well.

class SomeObject
  include Schnecke
  slug :name

  def before_assign_slug(opts={})
    puts 'Hello world! I get run before the slug assignment process'
  end

  def after_assign_slug(opts={})
    puts 'Goodbye world! I get run after the slug assignment process'
  end
end

Advanced Usage

If you need to change how the slug is generated, how duplicates are handled, etc., you can overwrite the methods in your class. For example to change how slugs are generated you can overwrite the slugify method.

class SomeObject
  include Schnecke
  slug :name

  # Overwrite the `slugify` method. In this case the slug will always be 'foo'
  def slugify(str)
    'foo'
  end
end

Note, by default the library will validate to ensure that the slug only contains lowercase alpphanumeric letters and '-' or '_'. If your new method changes the alloweable set of characters you can either disable this validation, or pass in your own validation pattern.

class SomeObject
  include Schnecke
  slug :name, require_format: false

  def slugify(str)
    'This#Would/NormallyF@!l'
  end
end

class SomeOtherObject
  include Schnecke
  slug :name, require_format: /\A[a-z]+\z/

  def slugify(str)
    'lettersonly'
  end
end

The methods that can be overwritten are

• slugify(str): This is used to turn a string into a slug
• slugify_blank: This is used when the slug returned is blank and we need some default slug generated
• slugify_duplicate(slug): This will take a slug generated by slugify and generate a unique version of it
• slug_concat(parts): This takes an array of slugs and combines them into 1 string

For details, please see the actual code.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/prschmid/schnecke.

Acknowledgements

This work is based on the slug gem.

License

The gem is available as open source under the terms of the MIT License.