I have a trigger to make rejection comments mandatory. I have many records that have already been approved/rejected without comments. When a user attempts to reject a record that has already been approved or reject AND HAS NO comments, they receive an error (RequireRejectionComment: execution of BeforeUpdate caused by: System.ListException: List index out of bounds: 0: Trigger.RequireRejectionComment: line 29, column 1).

trigger RequireRejectionComment on carrier__c (before update) {

  Map<Id, carrier__c> rejectedStatements = new Map<Id, carrier__c>{};

  for(carrier__c car: trigger.new)
    carrier__c oldcar = System.Trigger.oldMap.get(car.Id);

    if (oldcar.Approval_Status__c != 'Rejected' 
    && car.Approval_Status__c == 'Rejected')
        rejectedStatements.put(car.Id, car);
  for (ProcessInstance pi : [SELECT TargetObjectId, 
                                 SELECT Id, StepStatus, Comments 
                                 FROM Steps
                                 WHERE StepStatus = 'Rejected'
                                 ORDER BY CreatedDate DESC
                                 LIMIT 1 
                               FROM ProcessInstance
                               WHERE TargetObjectId In 
                               ORDER BY CreatedDate DESC
      ***if ((pi.Steps[0].Comments == null || pi.Steps[0].Comments.trim().length() == 0))***
          'Please enter a rejection comment!');

Your guidance is much appreciated.

1 Answer 1


As far as I can see and understand your logic and code ar correct. The only thing I can think of is adding an additional condition to verify the list isn't empty.

if (
    && (pi.Steps[0].Comments == null || pi.Steps[0].Comments.trim().length() == 0)

but if we're not sure what data scenario does end up in your query, yet having no Step records, this could introduce a bug...

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