Trigger to Increment the Number value when new Lead is created when Lead Country is india

Question

My requirement is that when i create a lead with country as 'india', there is a custom field named 'India_Auto_Number__c' where it should update as 1, and again when i create a lead with country name 'india' it should increment to 2...like this it should keep on incrementing till 5th lead, when i try to insert 6th lead, it should again update as 1 how do i achieve this functionality i went through below links but still i could not achieve the functionality any help would be highly appriciated

How to generate auto number using triggers

i have tried the trigger

    trigger LeadIncrementV2 on Lead (before insert,Before Update) {


    Lead lds = new Lead();

    Lead ld = [SELECT India_Auto_Number__c  from Lead LIMIT 1];

    integer LatestNumber = Integer.valueOf(lds.India_Auto_Number__c);

    for(Lead llds : Trigger.New){
        if(Trigger.OldMap.get(llds.id).Country == 'India'){ // i am getting an error as " Null Pointer Exception"

            llds.India_Auto_Number__c = LatestNumber + 1;
            // India_Auto_Number__c is an custom number field
        }
    }

    lds.India_Auto_Number__c= LatestNumber + 1;
    update lds;        

}

Answer 1

There are couple of issues with your code:

1. Trigger.oldmap is not available at the time of insert.
2. SOQL query should fetch the latest India_Auto_Number__c from the database to decide what number should be assigned to new lead.

Based on above points, below are the changes I did in your code:

trigger LeadIncrementV2 on Lead (before insert, Before Update) {
    if (Trigger.isbefore) {
      integer LatestNumber = 1;
      List<Lead> lds = [SELECT India_Auto_Number__c  from Lead where Country = 'India' Order by India_Auto_Number__c desc LIMIT 1];
      if (lds != null && lds.size () > 0) {
        LatestNumber = Integer.valueOf (lds[0].India_Auto_Number__c);
        LatestNumber++;
      }

      for (Lead llds : Trigger.New) {
          if (llds.Country == 'India') { 
              if (LatestNumber == 5)
                LatestNumber = 1;
              llds.India_Auto_Number__c = LatestNumber;
              LatestNumber ++;
          }
      }
    }
}

Please note that above logic is not tested however it should give you fair amount of idea.