How should I handle model attribute that doesn't match request params?

Question

I have a model like this...

Receipt
-------
amount:int  # => An amount of money stored as cents.

But in the view I have these fields...

amount_dollars
amount_cents

So mass assignment won't work there.

What is the standard way to deal with this situation? Where do you put the code that converts the incoming values into an amount of cents?

Answer 1

add attr_accessors for amount_dollars and amount_cents. use a before_save callback to update amount.

Answer 2

You can define a so-called virtual attribute for each of these fields in the view.

def amount_dollars=(value)
  ...
end

def amount_cents=(value)
  ...
end

These handle the values that come from the form submitted. In each of these methods you modify your model's amount attribute appropriately.

Answer 3

You may be looking for virtual attributes?

There's a railscast about it.

You can watch it here.

There's also the text-based version of it in case you like it better.