How to validate numericality and inclusion while still allowing attribute to be nil in some cases?

Question

In a Rails app I have several integer attributes on a model.

A user should be able to create a record and leave these attributes blank.

Or, if the user ente

Answer 1

You can add an :allow_nil => true to your validates_numericality_of.

validates_numericality_of :a, :only_integer => true, :allow_nil => true, 
    :message => "can only be whole number."

You can also use greater_than_or_equal_to and less_than_or_equal_to options if you just want to use one validation:

validates_numericality_of :a, :only_integer => true, :allow_nil => true, 
    :greater_than_or_equal_to => 1,
    :less_than_or_equal_to => 999,
    :message => "can only be whole number between 1 and 999."

Answer 2

should be simply:

validates_numericality_of :a, :only_integer => true, :message => "can only be whole number.", :allow_nil => true

same for the second validation