Rails Undefined Method when Trying to Divide

I have what should be a simple operation where I want to calculate the percentage completion of something in Rails 3.

In my Object model, I have the following function:

def balance
  (self.amount_remaining / self.amount) * 100
end

开发者_Python百科Then, in my Object view, I have the following:

<%= Object.balance %>

However, I get the following error:

undefined method `/' for nil:NilClass

Does anyone know what may be causing this error? Should I be making this calculate elsewhere?

---

Like this?

(self.amount_remaining / self.amount) * 100 rescue 0