How to temporarily change the default value of column?

I have a model which contains many predefined rows (> 100) and also can be edited by the user. I want to distinguish between pre-defined and user-added rows.

Because the database will be edited by a third-party application, too, I want to be on the safe side and set the default value for predefined to false in the database schema, because setting it to true will lead to serious re开发者_如何转开发strictions on the row (i.e. it can never be deleted)

On the other hand the install script which creates the > 100 predefined rows now has to specify predefined = true for every row, which clutters the script.

It's not that bad, but if there's a simple way to change the default way from Rails it would make my script look more friendly.

In other words: I want to write this:

MyModel.create(:data => "value")

but what I want to happen is this:

MyModel.create(:data => "value", :predefined = true)

Is this possible?

EDIT: This is only an examply, actually there are some more columns I have to set differently for predefined columns.

You could do it two different ways :

In your migrations :

t.column :boolean :string, :default => true

It defines the default value to true directly in the database. When you change it, you have to create a new migration.

In your model :

def before_create
    predefined = true if predefined.nil?
end

It defines the value to "true" unless you already defined it to something else. You can change the value just by changing it in the model.