Rails模型属性允许为nil，但不允许时进行验证

Question

I want to validate an input box value in two cases:

1. If nil? then save successfully, no errors
2. If not nil? then validate its format

I have a simple line here:

validates :ip_addr, format: { with: Regexp.union(Resolv::IPv4::Regex)}

This will work in all cases but won't allow a nil/empty value as it throws an exception. But:

validates :ip_addr, format: { with: Regexp.union(Resolv::IPv4::Regex)}, allow_nil: true

and

validates :ip_addr, format: { with: Regexp.union(Resolv::IPv4::Regex)}, allow_blank: true

Will allow nil/empty values but If the input is invalid eg "33@@@#$" then it returns "true".

How could I include both cases ? Is that possible ?

EDIT: It seems that Regexp.union(Resolv::IPv4::Regex).match("something") returns nil so If the validation works the same way, it will return nil in wrong values and allow_nil: true will allow them to be persisted like this.

Answer 1

Try this

validates :ip_addr, format: { with: Regexp.union(Resolv::IPv4::Regex)}, if: :ip_addr

I am not sure whether the above one will work. If it doesn't, do this

validate :ip_addr_format_check, if: :ip_addr

def ip_addr_format_check
  unless ip_addr =~ Regexp.union(Resolv::IPv4::Regex)
    errors.add(:base, "Error you want to show")
  end
end

Answer 2

Typecasting seems to be the problem.

The solution below works fine:

validates :ip_addr, format: { with: Resolv::IPv4::Regex }, 
    presence: false, unless: Proc.new { |ifc| ifc.ip_addr_before_type_cast.blank? }

Most probably we need to check If the variable's value is blank before casting it to inet (postgreSQL).