Is it possible to pass params from to a before_create in a model?

Question

I have a model, for example :

class Account < ActiveRecord::Base

  before_create :build_dependencies

  def build_dependencies
    # use nifty params to build this related object
    build_nifty_object(params)
  end

The initial params are sent in through a hidden form tag on the Account#new form.

But there's no reason/need for these params to be saved to the account model. I just need them in the NiftyObject model.

Is there a clever way to pass these params to the before_create method ? Or any other alternatives that might accomplish the same task?

Thanks!

The param hash is normally used in the controller to create your model object. How is niftyObject related to your Account Model? In your code example, we cannot see a belong_to or something indicating you have a relation between theses two objects? — Cygnusx1, Jun 27 '12 at 15:06

Matzi · Accepted Answer · 2012-06-27T17:04:59.927

3

You can use instance variables to workaround this, and do +1 step from the controller:

class Account < ActiveRecord::Base

  before_create :build_dependencies

  def assign_params_from_controller(params)
    @params = params
  end

  def build_dependencies
    # use nifty params to build this related object
    build_nifty_object(@params)
  end

In the controller:

  def Create
    account = new Account(params)
    account.assign_params_from_controller( ... )
    account.save   # this will trigger before_create
  end

edited Jun 27 '12 at 17:04

answered Jun 27 '12 at 15:05

Matzi

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Hmm.. question: how would I apply `assign_params_from_controller(params)` ? – Trip Jun 27 '12 at 15:16
1

In your controller, you call this before saving the Account instance. – Matzi Jun 27 '12 at 15:22
I just realized this wouldn't work because methods in the model are only available for specific objects. Since this would be before_create, I can't think of a way to make it global. – Trip Jun 27 '12 at 16:06
`Before_create` is running when you first *save* the model, not when you create it with a new. Check the example. Description: http://railstalk.com/?p=39 – Matzi Jun 27 '12 at 17:04
This would never work though : `Account.assign_params_from_controller(params)`. It would have to be : `Account.find(x).assign_params_from_controller(params)` . But since its before_create, I have nothing to choose. – Trip Jun 27 '12 at 18:27
1

Look the example again. First step, an account is created. Second step, the function is called on this instant. Third step, it is saved, which triggers the before_create. As you can see, the lower case `account` is an instantiated object, not the Account class. With the class, it wouldn't work, but with the newly kcreated object it will work. – Matzi Jun 27 '12 at 19:36
Ahhhhh genius! How did I miss that! Thanks! – Trip Jun 27 '12 at 19:44

score 2 · Answer 2 · answered Jun 27 '12 at 15:12

I believe the active-record callback cycle hurts you in most cases, this included. Instead of using before_create, I recommend you use a service object that coordinates the creation of Account and nifty-object.

I assume you want nifty-object to know about the account, so I passed it in to it's create method.

class CreatesAccount
  def self.create(params)
    account = Account.new(params)
    return account unless account.valid?
    ActiveRecord::Base.transaction do
      account.save!
      NifyObject.create(params, account: account)
      return account
    end
  end
end

score 2 · Answer 3 · answered Jun 27 '12 at 16:22

2

I appreciate everyone's answers. But I finally am going with an attr_accessor instead. In this way, it doesn't save anything anywhere, but would still be accessible from the model in a before_create method.

answered Jun 27 '12 at 16:22

Trip

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Is it possible to pass params from to a before_create in a model?

3 Answers3

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