Rails 5.0.1 - Friendly_id gem - included active concern module before_create or before_save

Question

I have created this module:

app/models/concerns/sluggable.rb

module Sluggable
  extend ActiveSupport::Concern

  included do
    before_create :set_slug
  end


  def set_slug
    if self.slug.nil?
      puts 'adding slug'
      self.slug = SecureRandom.urlsafe_base64(5)
    end
  end

end

and I include it in a model, like so:

app/models/plan.rb

class Plan < ApplicationRecord
  extend FriendlyId
  friendly_id :id, :use => :slugged
  include Sluggable
end

but the before_create does not fire. The slug column is a not_null column so I get a database error.

ERROR: null value in column "slug" violates not-null constraint

If put the set_slug code directly in the model, it works. So what am I missing here about Concerns in Rails 5?

I wonder if its something related to using FriendlyId (which is why I added slugs in the first place!)

set_slug should not be a class method. Just write it as a normal method inside the sluggable module. — Pedro Nascimento, Feb 18 '17 at 19:53
That is what I tried first. Same problem - I've updated the question to put the code back to how I first had it (ie. not as a class method) — rmcsharry, Feb 18 '17 at 20:06
Also you mention that if you add `set_slug` to the model works. So leaving the `included do...end` in the module and just copying set_slug works? — Pedro Nascimento, Feb 18 '17 at 20:25
before_save does not work. If I copy the before_create hook AND the set_slug it works - I need to copy both — rmcsharry, Feb 18 '17 at 20:44
FYI if I leave the hook in the module, include it and put only the set_slug method in the model, that works. Weird, huh? — rmcsharry, Feb 18 '17 at 20:46
Could you try only moving the before_create hook and see if it works? I think the issue is with the `included` block. — Pedro Nascimento, Feb 18 '17 at 20:46
I tried that too. I believe the issue is related to FriendlyId gem. I think set_slug might be a method it also uses. — rmcsharry, Feb 18 '17 at 20:51

score 1 · Accepted Answer · answered Feb 18 '17 at 21:00

This helped me solve this. Friendly_Id sets the slug in a before_validation callback if it is nil.

So my module needs to 'jump' in ahead of that. So the solution to make a module that doesn't conflict with Friendly_id is as below.

Notice I need to change the method name for my hook (as set_slug is a method used by Friendly_Id) AND I have to use prepend: true. Together this causes my code to set the slug before Friendly_Id fires its check to try and set it.

module Sluggable
  extend ActiveSupport::Concern

  included do
    before_validation :set_a_slug, prepend: true
  end


  def set_a_slug
    if self.slug.nil?
      self.slug = SecureRandom.urlsafe_base64(5)
    end
  end

end

Rails 5.0.1 - Friendly_id gem - included active concern module before_create or before_save

1 Answers1