LeadHandler

LeadHandler.cls

public with sharing class LeadHandler {
    public static void handleAfterInsert(List<Lead> newLeads){  
        List<Task> newTasks = new List<Task>();
        for (Lead l : newLeads){
            
            Task t = new Task();
            t.WhoId = l.Id;
            switch on l.ProductInterest__c{
            	when 'Cookbook Authorship'{
            		t.Subject = 'Follow up About Cookbook Authorship';
                } when 'Cookbook Editing'{
                    t.Subject = 'Follow up About Cookbook Editing';
                } when 'Cookbook Distribution'{
                    t.Subject = 'Follow up About Cookbook Distribution';   
                } when else {
                    t.Subject = 'Other';   
                }
            }
            newTasks.add(t);
          }
        insert newTasks;
    }
    
    public static void handleAfterUpdate(List<Lead>newLeads, Map<Id, Lead>oldLeadMap){
        List<Task> newTasks = new List<Task>();
        for (Lead newLead : newLeads){
            Lead oldLead = oldLeadMap.get(newLead.Id);
            if (newLead.ProductInterest__c != oldLead.ProductInterest__c){  
                Task t = new Task();
                t.WhoId= newLead.Id;
                t.Subject = 'Follow up About Product Interest Change';
                newTasks.add(t);
          	}
        }
     	insert newTasks;
    }
 }

Great job @niavesper! 👏 Using switch might be an overkill on this scenario as you can assign subject with 'Follow up ' + lead.Product_Interest__c with one line but other than that looks awesome!

@tugce Thank you for the great tip. I was going to use nested if statements at first, then opted for a switch to make it a bit more efficient, but your suggestion is much better. Thank you again!