how to add model validation with condition in ruby

Question

I am trying to do model validation for gstno only if the selected country equals India, please help, i tried like this not working

validates :gstno, uniqueness: true, :format => {:with => /[0-9]{2}[A-Z]{5}[0-9]{4}[A-Z]{1}[1-9A-Z]{1}Z[0-9A-Z]{1}/, :message => 'INCORRECT FORMAT!'} if self.country =='IN'

error is like this

undefined method `country' for #<Class:0x007fb021d6a0c8> Did you mean? count

Answer 1

您能否尝试以下代码：

validates :gstno, uniqueness: true, :format => {:with => /[0-9]{2}[A-Z]{5}[0-9]{4}[A-Z]{1}[1-9A-Z]{1}Z[0-9A-Z]{1}/, :message => 'INCORRECT FORMAT!'}, if: -> { country == 'IN' }

Answer 2

You probably want to move this to a custom validation method

https://guides.rubyonrails.org/active_record_validations.html#custom-methods

self will be available to you there