Validate Rails attribute presence but allow empty string

Question

I want to validate a string attribute is not nil, but allow empty strings.

As in:

validates name: not_nil, allow_empty: true

Answer 1

you could also do:

validates :name, exclusion: { in: [nil] }

Answer 2

To allow an empty string, but reject nil in an active record validation callback, use a conditional proc to conditionally require the presence of the attribute if it's not nil.

So the code looks like:

validates :name, presence: true, if: proc { name.nil? }

But you probably want to allow null. Then don't validate. Still check for presence? in code for nil or empty string.