ruby - How can I format the value shown in a Rails edit field?

Question

I would like to make editing form fields as user-friendly as possible. For example, for numeric values, I would like the field to be displayed with commas (like number_with_precision).

This is easy enough on the display side, but what about editing? Is there a good way to do this?

I am using the Rails FormBuilder. Upon investigation, I found that it uses InstanceTag, which gets the values for fields by using <attribute>_value_before_type_cast which means overriding <attribute> won't get called.

Answer 1

The best I have come up with so far is something like this:

<%= f.text_field :my_attribute, :value => number_with_precision(f.object.my_attribute) %>

Or my_attribute could return the formatted value, like this:

def my_attribute
  ApplicationController.helpers.number_with_precision(read_attribute(:my_attribute))
end

But you still have to use :value

<%= f.text_field :my_attribute, :value => f.object.my_attribute %>

This seems like a lot of work.