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module FriendlyId
# @guide begin
#
# ## History: Avoiding 404's When Slugs Change
#
# FriendlyId's {FriendlyId::History History} module adds the ability to store a
# log of a model's slugs, so that when its friendly id changes, it's still
# possible to perform finds by the old id.
#
# The primary use case for this is avoiding broken URLs.
#
# ### Setup
#
# In order to use this module, you must add a table to your database schema to
# store the slug records. FriendlyId provides a generator for this purpose:
#
# rails generate friendly_id
# rake db:migrate
#
# This will add a table named `friendly_id_slugs`, used by the {FriendlyId::Slug}
# model.
#
# ### Considerations
#
# Because recording slug history requires creating additional database records,
# this module has an impact on the performance of the associated model's `create`
# method.
#
# ### Example
#
# class Post < ActiveRecord::Base
# extend FriendlyId
# friendly_id :title, :use => :history
# end
#
# class PostsController < ApplicationController
#
# before_filter :find_post
#
# ...
#
# def find_post
# @post = Post.friendly.find params[:id]
#
# # If an old id or a numeric id was used to find the record, then
# # the request slug will not match the current slug, and we should do
# # a 301 redirect to the new path
# if params[:id] != @post.slug
# return redirect_to @post, :status => :moved_permanently
# end
# end
# end
#
# @guide end
module History
module Configuration
def dependent_value
dependent.nil? ? :destroy : dependent
end
end
def self.setup(model_class)
model_class.instance_eval do
friendly_id_config.use :slugged
friendly_id_config.class.send :include, History::Configuration
friendly_id_config.finder_methods = FriendlyId::History::FinderMethods
FriendlyId::Finders.setup(model_class) if friendly_id_config.uses? :finders
end
end
# Configures the model instance to use the History add-on.
def self.included(model_class)
model_class.class_eval do
has_many :slugs, -> { order(id: :desc) }, **{
as: :sluggable,
dependent: @friendly_id_config.dependent_value,
class_name: Slug.to_s
}
after_save :create_slug
end
end
module FinderMethods
include ::FriendlyId::FinderMethods
def exists_by_friendly_id?(id)
super || joins(:slugs).where(slug_history_clause(id)).exists?
end
private
def first_by_friendly_id(id)
super || slug_table_record(id)
end
def slug_table_record(id)
select(quoted_table_name + ".*").joins(:slugs).where(slug_history_clause(id)).order(Slug.arel_table[:id].desc).first
end
def slug_history_clause(id)
Slug.arel_table[:sluggable_type].eq(base_class.to_s).and(Slug.arel_table[:slug].eq(id))
end
end
private
# If we're updating, don't consider historic slugs for the same record
# to be conflicts. This will allow a record to revert to a previously
# used slug.
def scope_for_slug_generator
relation = super.joins(:slugs)
unless new_record?
relation = relation.merge(Slug.where("sluggable_id <> ?", id))
end
if friendly_id_config.uses?(:scoped)
relation = relation.where(Slug.arel_table[:scope].eq(serialized_scope))
end
relation
end
def create_slug
return unless friendly_id
return if history_is_up_to_date?
# Allow reversion back to a previously used slug
relation = slugs.where(slug: friendly_id)
if friendly_id_config.uses?(:scoped)
relation = relation.where(scope: serialized_scope)
end
relation.destroy_all unless relation.empty?
slugs.create! do |record|
record.slug = friendly_id
record.scope = serialized_scope if friendly_id_config.uses?(:scoped)
end
end
def history_is_up_to_date?
latest_history = slugs.first
check = latest_history.try(:slug) == friendly_id
if friendly_id_config.uses?(:scoped)
check &&= latest_history.scope == serialized_scope
end
check
end
end
end
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