Populate Lookup field on Opportunity upon Lead Conversion

Question

I am trying to populate a Contact lookup field (Sourced_By__c) on the Opportunity with the Converted Contact upon Lead Conversion but am not having any luck. I do not get an error but it also does not populate the field. Here is my trigger below, can anyone help?

Trigger Lead on Lead (before update) {

    if (Trigger.isBefore) {

        if (Trigger.isUpdate) { 

            Set<Id> setLeadIds     = new Set<Id>();  
            Set<Id> setConvertedOppIds   = new Set<Id>();
            Set<Id> setConvertedContIds   = new Set<Id>();  

            for (Lead ld : Trigger.new) {

                // Find all converted Leads with Opportunitiy and add ConvertedOpportunityId to setConvertedOppIds
                if (ld.isConverted && ld.ConvertedOpportunityId != null 
                    && Trigger.oldMap.get(ld.Id).ConvertedOpportunityId != ld.ConvertedOpportunityId) 
                    setConvertedOppIds.add(ld.ConvertedOpportunityId);  

                 // Find all converted Leads with Contacts and add ConvertedContactId to setConvertedContIds    
                if (ld.isConverted && ld.ConvertedContactId != null 
                    && Trigger.oldMap.get(ld.Id).ConvertedContactId != ld.ConvertedContactId) 
                    setConvertedContIds.add(ld.ConvertedContactId);         
            }  

       if (!setConvertedOppIds.isEmpty()) {

                List<Opportunity> lstOpp = new List<Opportunity>();
                for(Opportunity opps:[select Id,AccountId,CampaignId from Opportunity where Id in :setConvertedOppIds])

                List<Contact> lstCont = new List<Contact>();
                for(Contact Conts:[select Id,AccountId from Contact where Id in :setConvertedContIds])

                  if (lstOpp.size() > 0) {                  
                    for (Opportunity opp : lstOpp) {
                        Opportunity otm = new Opportunity(
                                   //OpportunityId  = opps.Id,
                                   Sourced_By__c  = Conts.Id);
                        lstOpp.add(otm);
                    }
                                        if (!lstOpp.isEmpty()) {Update lstOpp;
                                               }


            }
        }       
    }   
}
   }

Answer 1

Try this out:

Trigger Lead on Lead (after update) {

    if (Trigger.isAfter) {

        if (Trigger.isUpdate) { 

            Map<ID,ID> oppToContact = new Map<ID,ID>(); 

            for (Lead ld : Trigger.new) {
                if(ld.isConverted && trigger.oldMap.get(ld.id).isConverted) continue; //only process newly converted leads

                // Find all converted Leads with Opportunitiy and add ConvertedOpportunityId to setConvertedOppIds
                if (ld.ConvertedOpportunityId != null && ld.ConvertedContactId != null){                    
                    oppToContact.put(ld.ConvertedOpportunityId,ld.ConvertedContactID);  

                }

            }  

       if (!oppToContact.isEmpty()) {

                List<Opportunity> lstOpp = new List<Opportunity>();
                for(Opportunity opps:[select Id,AccountId,CampaignId from Opportunity where Id in :oppToContact.keySet()]){

                    if(oppToContact.containsKey(opps.id)){
                        opps.Sourced_By__c = oppToContact.get(opps.id);
                        lstOpp.add(opps);
                    }

                }
        }

        if (!lstOpp.isEmpty()) {
          Update lstOpp;
         }

    }
}

Answer 2

Plus 1 for Eric's answer.

Depending on your requirements, you might be able to simplify it a bit and save a SOQL query in the trigger context.

trigger LeadTrigger on Lead (after update) {

    if (trigger.isAfter && trigger.isUpdate) {
        List<Opportunity> oppsToUpdate = new List<Opportunity>();

        for (Lead ld : triggerNew) {
            if(ld.isConverted && triggerOldMap.get(ld.id).isConverted) {
                continue; //only process newly converted leads
            }

            if (ld.ConvertedOpportunityId != null && ld.ConvertedContactId != null) {
                 Opportunity opp = new Opportunity(Id = ld.ConvertedOpportunityId);
                 opp.Sourced_By__c = ld.ConvertedContactID;
                 oppsToUpdate.add(opp);
            }
        }

        if (!oppsToUpdate.isEmpty()) {
            update oppsToUpdate;
        }
    }

}