Rails: Validating min and max length of a string but allowing it to be blank

Question

I have a field that I would like to validate. I want the field to be able to be left blank, but if a user is entering data I want it to be in a certain format. Currently I am us

Answer 1

I think it might need something like:

validates_length_of :foo, minimum: 5, maximum: 5, allow_blank: true

More examples: ActiveRecord::Validations::ClassMethods

Answer 2

every validates_* accepts :if or :unless options

validates_length_of :foo, :maximum => 5, :if => :validate_foo_condition

where validate_foo_condition is method that returns true or false

you can also pass a Proc object:

validates_length_of :foo, :maximum => 5, :unless => Proc.new {|object| object.foo.blank?}

Answer 3

Add in your model:

validates :color, length: { is: 7 }

color is a string:

t.string :color, null: false, default: '#0093FF', limit: 7