ruby on rails - validates_presence_of at least one of these associations -

a withdrawalaccount record contains either sepaaccount, internationalaccount, paypalaccount or otheraccount. should @ least 1 of these. can not more one.

class withdrawalaccount < activerecord::base   has_one :sepa_account   has_one :international_account   has_one :third_account   has_one :fourth_account end 

updated question: how can validate_presence_of either 1 of them while allowing 1 of them present.

try:

class withdrawalaccount < activerecord::base   has_one :sepa_account   has_one :international_account    validates :sepa_account,          presence: true, if: ->(instance) { instance.international_account.blank? }   validates :international_account, presence: true, if: ->(instance) { instance.sepa_account.blank? } end 

to validate either 1 should prefer following method:

class withdrawalaccount < activerecord::base    validate :accounts_consistency    private    def accounts_consistency     # xor operator more information here http://en.wikipedia.org/wiki/xor     unless sepa_account.blank? ^ international_account.blank?       errors.add(:base, "options consistency error")     end   end end 

with more 2 attributes validate:

since xor not work more 2 attributes (a ^ b ^ c) check attributes using loop:

def accounts_consistency   attributes = [sepa_account, international_account, third_account, fourth_account]   result = attributes.select |attr|     !attr.nil?   end    unless result.count == 1     errors.add(:base, "options consistency error")   end end