Rails 3: Validations for object - ruby-on-rails-3

Question

I'm creating an object via controller. A Foo has many Bars. The Bar model has a validation that it must have a Foo in order to be valid.
In the foo.rb model:
has_many: bars
In the bar.rb model:
validates_presence_of :foo
belongs_to: foo
In the foo_controller.rb:
#foo = Booking.new(params[:foo]) # this has all the params needed to make a Foo.
#foo.create_bars(params[:bars])
In the foo.rb model:
def create_bars(bars)
bars.each do |t|
bar = Bar.create({name: name, email: email, foo: foo})
bar.foo = self
self.bars << bar
bar.save
puts self.bars.to_s
end
end
The puts self.bars.to_s
This sounds like it should be something really basic, but since the foo doesn't exist in the db, does ActiveRecord consider it to be nil, and that's why it's not saving? How can I write this properly?

Answer 1

Maybe try this:
def create_bars(bars)
bars.each do |t|
self.bars << Bar.new({name: t[:name], email: t[:email]})
end
end
<< operator used for active record objects sets association automatically.
Do not forget to add has_many :foos, and belongs_to :bar in the models.

Answer 2

I'll answer this part first:
This sounds like it should be something really basic, but since the
foo doesn't exist in the db, does ActiveRecord consider it to be nil,
and that's why it's not saving? How can I write this properly?
Not quite. The validation doesn't depend on anything in the database, it merely checks whether the specified field (or dependent object) is present in the model before persisting. The create method is a kind-of shortcut that not only initializes an ActiveModel object, but also simultaneously attempts to save it in the database. Your validation is failing because you're calling this method BEFORE you've set the foo field of your bar object.
You can technically use create in this instance by passing foo: self in your scenario, but frankly I would go with #pablopablo89's answer in regards to this part. If you do it this way, when you save Foo, all the Bar objects will also get saved.
Additionally, the .create method for creating Bar objects is dangerous because, since you're immediately persisting Bar objects independent of the parent Foo, if for whatever reason your Foo cannot be saved (fails some other validation, etc etc), you end up with a bunch of orphaned Bar objects with no way to remove them independent of a Foo (I'm making a bit of an assumption of how your system actually works). Assuming this is a reflection of your system, the goal you want to keep in mind is that an object, and all of its dependencies, are saved in one atomic operation. If one fails, they all fail, and you alert the user.
To answer the question more generally, as #phoet pointed out in the comment, you might be a lot better off changing your form and using the accepts_nested_attributes_for method. Here is the link to the rails documentation.
In the Foo model, add the line accepts_nested_attributes_for :bars, and then use fields_for in the form, something like this:
<%= form_for #foo do |f| %>
...other stuff...
<%= f.fields_for :bars do |f_bar| %>
... bar-related stuff ...
The submitted parameter map will return with all the bar-related stuff within the :foo key in such a way that it will create both the Foo object, and all of the related Bar objects all at once. In that scenario, create will also work, although I still tend to do separate .new and .save, but its up to you.
This link regarding how to use fields_for might be helpful as well.

Answer 3

Booking.new just initializes an object. In order for foo to exist you need to save it. Once you save it your validation while creating bar objects will pass and the objects should be created. Hopefully this should work