Ruby-on-rails – ActiveRecord Callbacks List

activerecordcallbackruby-on-rails

I've been going through the rails source for a while now, and I don't think there's a better way of getting the list of all callbacks other than: ActiveRecord::Callbacks::CALLBACKS – which is a constant list.

Meaning if you're using a gem like devise_invitable that adds a new callback called :invitation_accepted with the score :after and :before then ActiveRecord::Callbacks::CALLBACKS will not work.

Do you know of an easy fix, other than opening up rails modules and making sure there's an internal list of call-backs per model class?

Best Answer

You can call Model._save_callbacks to get a list of all callbacks on save. You can then filter it down to what kind you need e.g. :before or :after like this:

Model._save_callbacks.select {|cb| cb.kind == :before}

Works the same for Model._destroy_callbacks etc.

Related Solutions

Ruby-on-rails – Rails: How to set default values in ActiveRecord

There are several issues with each of the available methods, but I believe that defining an after_initialize callback is the way to go for the following reasons:

default_scope will initialize values for new models, but then that will become the scope on which you find the model. If you just want to initialize some numbers to 0 then this is not what you want.
Defining defaults in your migration also works part of the time... As has already been mentioned this will not work when you just call Model.new.
Overriding initialize can work, but don't forget to call super!
Using a plugin like phusion's is getting a bit ridiculous. This is ruby, do we really need a plugin just to initialize some default values?
Overriding after_initialize is deprecated as of Rails 3. When I override after_initialize in rails 3.0.3 I get the following warning in the console:

DEPRECATION WARNING: Base#after_initialize has been deprecated, please use Base.after_initialize :method instead. (called from /Users/me/myapp/app/models/my_model:15)

Therefore I'd say write an after_initialize callback, which lets you default attributes in addition to letting you set defaults on associations like so:

  class Person < ActiveRecord::Base
    has_one :address
    after_initialize :init

    def init
      self.number  ||= 0.0           #will set the default value only if it's nil
      self.address ||= build_address #let's you set a default association
    end
  end

Now you have just one place to look for initialization of your models. I'm using this method until someone comes up with a better one.

Caveats:

For boolean fields do:

self.bool_field = true if self.bool_field.nil?

See Paul Russell's comment on this answer for more details
If you're only selecting a subset of columns for a model (ie; using select in a query like Person.select(:firstname, :lastname).all) you will get a MissingAttributeError if your init method accesses a column that hasn't been included in the select clause. You can guard against this case like so:

self.number ||= 0.0 if self.has_attribute? :number

and for a boolean column...

self.bool_field = true if (self.has_attribute? :bool_value) && self.bool_field.nil?

Also note that the syntax is different prior to Rails 3.2 (see Cliff Darling's comment below)

Ruby-on-rails – Renaming model association attributes in Rails JSON serialization

Trying to generate complex JSON with the built-in options for as_json is clumsy. I would override as_json in your models, and not bother with calling super at all. Make up your own option keys for as_json to control what you want to include in the Hash.

# employee.rb
def as_json(options = {})
  json = {:name => name, ...} # whatever info you want to expose
  json[:business] = vendor.as_json(options) if options[:include_vendor]
  json
end

Best Answer

Related Solutions

Ruby-on-rails – Rails: How to set default values in ActiveRecord

Ruby-on-rails – Renaming model association attributes in Rails JSON serialization

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