Apex Trigger for Adding Contacts to Campaigns as Campaign Members

Question

I am writing an Apex Trigger that will take the Primary_Contact__c from an Opportunity that has been Closed Won and the Amount != Null and add that Contact to a Campaign called Closed Won.

Primary_Contact__c is a Lookup field to the Contact object and has a relationship name of Primary_Contact__r.

Below is the code that I currently have. It is not throwing any errors it is just not adding the Contact to the proper Campaign upon saving of the record.

trigger UpdateClosedWonMembers on Opportunity (before update) {
List<CampaignMember> members = new List<CampaignMember>();

for (Opportunity opp : Trigger.new) {
    if (opp.StageName == 'Closed Won' && opp.Amount != Null) {
        CampaignMember cm = new CampaignMember(CampaignId = '7011a000000BBny', ContactId = opp.Primary_Contact__r.Id, Status = 'Sent');

        members.add(cm);
    }

    try{
        insert members;
    } catch(DmlException e) {
        System.debug('An unexpected error has occured: ' + e.getMessage());
    }
}
}

Answer 1

The reason for the error has to do with context:

CampaignMember cm = new CampaignMember(CampaignId = '7011a000000BBny',
                      ContactId = opp.Primary_Contact__r.Id, Status = 'Sent');

When the trigger executes the values of lookup fields are not available in Trigger.new. If you need Lookup fields (or children) you have to SOQL query them

opp.Primary_Contact__r.Id

Instead, change the line to

CampaignMember cm = new CampaignMember(CampaignId = '7011a000000BBny',
                      ContactId = opp.Primary_Contact__c, Status = 'Sent');

As an aside -- never use hard coded ids as they cause all sorts of deployment issues. Instead, query for the CampaignId