Rails Model Validation Conditional allow_nil?

Question

So I was wondering if we can have a conditional allow_nil option for a validation on a rails model. What I would like to do is to be able to allow_nil depending upon some logic(some other attribute) So I have a product model which can be saved as draft. and when being saved as draft the price can be nil, but when not a draft save the price should be numerical. how can I achieve this. The following doesn't seem to work. It works for draft case but allows nil even when status isn't draft. ``` class Product<ActiveRecord::Base attr_accessible :status, price validates_numericality_of :price, allow_nil: :draft? def draft? self.status == "draft" end end ``` Looking at rails docs I looks like there isn't an option to pass a method to allow_nil? One possible solution is to do separate validations for both cases ``` with_options :unless => :draft? do |normal| normal.validates_numericality_of :price end with_options :if => :draft? do |draft| draft.validates_numericality_of :price, allow_nil: tru…

Accepted Answer

You can use `if` and `unless` to do the following

```
class Product<ActiveRecord::Base
   attr_accessible :status, price
   validates_numericality_of :price, allow_nil: true, if: :draft?
   validates_numericality_of :price, allow_nil: false, unless: :draft?

def draft?
     self.status == "draft"
   end

end
```

With the above, you will have 2 validations set up, one that applies when `draft? == true`, which will allow nils, and one where `draft? == false` which will not allow nils

Rails Model Validation Conditional allow_nil?

Solution

Problem