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

rubyonrails-talk
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?