On Update, how can I validate that an attribute has not being already set?

Rails
1

Hi

I have a boolean attribute on a model … user_approved … that I
wish to apply some validation to upon update …

The business rule is “You cannot update this model to user_approved if
it already has been” … but I am not sure if I can do this using the
normal rails validations?

For example, using update_attributes, how do I tell that they have
requested to update this field as opposed to updating another?

Anyone have any elegant solutions?

Thanks
Shane

2

shane wrote:

The business rule is “You cannot update this model to user_approved if
it already has been” … but I am not sure if I can do this using the
normal rails validations?

You probably want to add this to the model:

attr_protected :user_approved

This will prevent the attribute from being set by #update_attributes and
so will protect you from someone sending their own form content to your
update actions and sneaking in a change.

You can then override the #user_approved= method in the model to do the
validation. When attributes are set, their #attribute= methods are
called to set the values. You can override these as you like to
validate the input and check the current value before making any
changes.

3

The business rule is fail.

If it’s already set to true, why does updating it true matter?

On Mon, Mar 3, 2008 at 9:32 AM, shane [email protected] wrote:

For example, using update_attributes, how do I tell that they have
requested to update this field as opposed to updating another?

Anyone have any elegant solutions?

Thanks
Shane

–
Ryan B.

Feel free to add me to MSN and/or GTalk as this email.