How to create a customised auto Number functionality through apex

Question

Am trying to create auto number through apex.

The functionality which i require there in an number field which is number/text type which is UNIQUE. Whenever an Account is created the custom number field should be incremented by 1 irrespective of the previous record are deleted the count should always keep on incrementing through a trigger. i can't use a auto number field type as there are different record types and the auto number field can't be incremented based on record type, the gap is okay and there shouldn't be no duplicates My code below.

trigger rectype on Account (before insert) {

        for(Account accitem : Trigger.New){


           Account acc = new Account();
           System.debug('rectype'+recordTypeId);
            List<Account> results =[SELECT <custom field>  FROM Account where  RecordTypeId='0120l000000PxdRAAS' order by CreatedDate desc LIMIT 1 ];
           Decimal prtnr =  results[0].custom field;

            System.debug('count'+prtnr);
            accitem.custom field= prtnr+1;
          //  i=integer.valueof(s);
            System.debug('PartnerId Visible'+accitem.<custom field>);
            }


}

The issue here is lets say the record is getting deleted , the incrementeation is happening from the recent record not with the last Customfield value.

From user3169951's comment:

i can't use a auto number filed type as there are different record types and the auto number field can't be incremented based on record type, the gap is okay and there shouldnt be no duplicates

Answer 1

By far the easiest and least error-prone approach is to base the logic on an auto-number field and then do further Apex processing (if that is needed) in an after trigger that applies its logic to the auto-number value and then updates a separate field with the final value.

There will be gaps in the numbering, but while you might be able to construct a reliable scheme to handle the most recent record(s) being deleted (for update would need to be used to avoid duplicates), recycling earlier numbers would be tough. So the effort is only worth it if no gaps in the numbering is an explicit and high-value requirement.

Answer 2

I normally use a custom setting for this. Just create a custom setting (list type, regardless of the warning SF gives), with one custom field, "Value". Create a record in this custom setting with name "Account Number" or something and with value 0. Then in your trigger get the current value for this record, assign the current value to your account and increment the value. This can be done in bulk of course.