Add callbacks to models dynamically

[jeffsaremi]

Is there a way to add callbacks such as "before_save" and such dynamically to all models before they 're actually used. This would be useful for tracing calls and object creation sequences.
I used something like this, even though I dont get any errors they're actually not called at all:

   3 class DBSeed
...
   12 ▏
   13 ▏ class << self
▎  14 ▏ ▏ def make_trace_proc(klass, sym)
▎  15 ▏ ▏ ▏ proc { puts ">>>#{klass.name} #{sym}" }
▎  16 ▏ ▏ end
▎  17 ▏ ▏ def create_tracing_callbacks
▎  18 ▏ ▏ ▏ symbols = [ "after_initialize", "before_create", "before_save", "before_update", "after_create", "after_save", "after_update"]
▎  19 ▏ ▏ ▏
▎  20 ▏ ▏ ▏ Mongoid.models.each do |m|
▎  21 ▏ ▏ ▏ ▏ klass = m.class
▎  22 ▏ ▏ ▏ ▏ symbols.each do |s|
▎  23 ▏ ▏ ▏ ▏ ▏ klass.send(:define_method, s, make_trace_proc(klass, s))
▎  24 ▏ ▏ ▏ ▏ end
▎  25 ▏ ▏ ▏ end
▎  26 ▏ ▏ end
   27 ▏ ▏ def run
...
▎  30 ▏ ▏ ▏ create_tracing_callbacks

[alexbevi]

Hi @jeffsaremi, as Mongoid has a dependency on ActiveModel, which in turn depends on ActiveSupport we can use an ActiveSupport::Concern similar to the following:

module TracingExtension
  extend ActiveSupport::Concern
  included do
    [:after_initialize, :before_create, :before_save, :before_update, :after_create, :after_save, :after_update].each do |callback|
      self.send(callback, proc { trace_callback(callback) })
    end

    protected
    def trace_callback(sym)
      puts ">>>#{self.class.name} #{sym}"
    end
  end
end

Using the above concern we can run a test with 2 models such as the following, which should trigger the associated callbacks as desired:

class Post
  include Mongoid::Document

  field :title, type: String
end

class User
  include Mongoid::Document

  field :name, type: String
end

Mongoid.models.each do |model|
  model.send(:include, TracingExtension)
end

Post.create! title: "My First Post"
u = User.new name: "Test"
u.save!
u.name = "Test2"
u.save!

Output:

>>>Post after_initialize
>>>Post before_save
>>>Post before_create
>>>Post after_create
>>>Post after_save
>>>User after_initialize
>>>User before_save
>>>User before_create
>>>User after_create
>>>User after_save
>>>User before_save
>>>User before_update
>>>User after_update
>>>User after_save

[jeffsaremi]

That's fantastic @alexbevi ! thank you so much for taking the time

[alexbevi]

My pleasure :)