How to unassign a value?

Answer 1

You can. But first, my assumptions:

1. I'm going to assume that you are using ActiveRecord and you have a model called MyModel in order to treat that table.
2. I'm going to assume that you used the proper way to make fields non-nullable, which is by using validations. If this is not the case, I strongly suggest that you reconsider using them.

Then you can do:

class MyModel < ActiveRecord::Base
  validates_pressence_of :name, :if => :check_name

  attr_writer :check_name
  def check_name # make it defalt to true
    @check_name = @check_name.nil? ? true : @check_name
  end
end

You can use it like this:

my_object.name = "Josh"
my_object.save # ok
my_object.name = ""
my_object.save # not ok
my_object.check_name = false
my_object.save # ok