Apex trigger which provides targets on sub campaign generates the error on parent campaign - salesforce

Question

I have a problem with one trigger. I was trying to set up the solution which will give me the possibility to assign flexible targets for campaigns. I was trying to solve it via formula field but it occurred to be too complex and I was advised it needs to be the apex trigger. I created the custom setting of list type, so then I could query it in the apex trigger. I created the "Apex_Calculator__c" field which combined values from two fields (Event Region [located on the parent campaign level] and Started Campaign [located on the sub-campaign level]). The value from the "Apex_Calculator__c" field was about to bring the same values as in the custom setting.
My knowledge of Apex triggers is limited, so I asked for the help on the internet. I received the help and the trigger was bringing target values in the sub campaign. However, the problem occurred on the parent campaign level. As far as I wanted to change the Event Region (which as I mentioned is part of the "Apex_Calculator__c" formula field), I started to receive the error message:
*
PopulateTarget: execution of BeforeUpdate caused by:
System.NullPointerException: Attempt to de-reference a null object:
Trigger.PopulateTarget: line 18, column 1
*
trigger PopulateTarget on Campaign (before insert, before update)
{
Map <String, Id> recordTypes = new Map <String, Id> ();
for (RecordType recordType : [SELECT Id, DeveloperName FROM RecordType WHERE sObjectType = 'Campaign'])
{
if (recordType.DeveloperName == 'Conference')
{
recordTypes.put(recordType.DeveloperName, recordType.Id);
}
}
for(Campaign campaign : Trigger.new)
{
// Make sure that the campaign record type is not in the map (in the map we keep the ones that we want to exclude)
if (recordTypes.get(campaign.RecordTypeId) == null && String.isNotBlank(campaign.Apex_Calculator__c) == true)
{
String target = DSTargets__c.getInstance(campaign.Apex_Calculator__c).Target__c;
campaign.DS_Target_Multiplier__c = Target;
}
}
}
I feel really lost what is wrong in here. Could anyone help me with this error?

Answer 1

Looks like you don't have DSTargets custom settings for some campaign.Apex_Calculator__c values.
Try this:
// Make sure that the campaign record type is not in the map (in the map we keep the ones that we want to exclude)
if (recordTypes.get(campaign.RecordTypeId) == null && String.isNotBlank(campaign.Apex_Calculator__c) == true)
{
if (DSTargets__c.getInstance(campaign.Apex_Calculator__c) == null)
{
System.debug('### A DSTargets named \'' + campaign.Apex_Calculator__c + '\' doesn't exist');
continue;
}
String target = DSTargets__c.getInstance(campaign.Apex_Calculator__c).Target__c;
campaign.DS_Target_Multiplier__c = Target;
}