Question

So I’ve implemented a hack and I want to know what the “proper” way is to do it.

The issue is that I have an *_attributes=() method that uses an instance variable. The reason this is a problem is that at the time the method is called, that instance variable hasn’t been set. Here is the method in question:

def proposed_times_attributes=(attributes)
  attributes.each do |key,value|
    value[:timezone] = timezone
  end
  assign_nested_attributes_for_collection_association(:proposed_times, attributes)
end

The timezone is in the params hash after proposed_times_attributes. Therefore my hack is to delete it from params, then add it back, thus moving it to the end of the line.

def create
  p = params[:consultation]
  a = p.delete(:proposed_times_attributes)
  p[:proposed_times_attributes] = a

  @consultation = current_user.advised_consultations.new(p)
  ...
end

What is the proper way that I should be doing this?

new() calls load() where the loop is that goes through each key/value pair.

Thankfully I’m using Ruby 1.9.2 which keeps the order, but it would be nice to know how to do this so that it wouldn’t depend on this fact.

Answer 1

If the next operation after new will always be a save operation, you can store the attributes in an accessor, and use a before_validation callback to operate on them as you wish.

class Consultations < ActiveRecord::Base

  attr_accessor :proposed_times_attributes

  before_validation :assign_proposed_times

  def assign_proposed_times
    proposed_times_attributes.each do |key,value|
      value[:timezone] = timezone
    end
    assign_nested_attributes_for_collection_association(:proposed_times, attributes)
  end

end

Now in your controller you simply have:

def create
  @consultation = current_user.advised_consultations.new(params[:consultation])
  ...
end

If you wish to do other operations before calling save, then pulling out the param as you did in your example, then passing it to an appropriate method after calling new would be the way to go.