RecipeHandlerClass.cls

/*Create a method that will be called before a recipe is inserted or updated */

public class RecipeHandlerClass
{

    //to check the missing key  values
    
    Public Static Void checkRecipeInformation( List<Recipe__c> newRecipies)
    {
        System.debug('newRecipies-->'+newRecipies);
        for(Recipe__c rec : newRecipies)
        {
            System.debug('rec-->'+rec);
            if(String.isblank(rec.Name)|| (rec.Active_Time__c == null) ||String.isblank(rec.Description__c)||(rec.Active_Time_Units__c== null )||(rec.Servings__c == null))
            {
                rec.Draft__c = TRUE;
            }
            else
            {
                rec.Draft__c = FALSE;
            }
        }
    }
    
    //Giving rating based on the return from helper method rateReciepecomplexcity//
    
   Public Static void complexityRate (List<Recipe__c> newRecipies)
   {
       for(Recipe__c rec : newRecipies)
       {
           Integer rating = Helperfunctions.rateRecipeComplexity(rec);
           if(rating== 1)
              {
                  rec.Complexity__c = 'Simple';
              }
            else if (rating== 2)  
            {
                   rec.Complexity__c = ' Moderate';
            }
            else if(rating ==3)
            {
                   rec.Complexity__c = 'Difficult';
            }                 
       }
   }


    // Create Review Task if it is not a draft recipe  and used in cookbook

    Public Static void createReviewTask (List<Recipe__c> newRecipies)
   {
      
        List<Recipe_Usage__c> recipeUsageList = [Select Name, Recipe__c , Cookbook__c, Cookbook__r.OwnerId
             from Recipe_Usage__c Where Recipe__r.Draft__c=false ] ;
        Set<Id> taskSet = new Set<Id>();   
        List<Task> taskList = new List<Task>();   
        for( Recipe_Usage__c recUsage: recipeUsageList)
        {
           Task task = new Task();           
           if(!taskSet.contains(recUsage.Cookbook__c)){
            task.OwnerId= recUsage.Cookbook__r.OwnerId;
            task.WhatId= recUsage.Cookbook__c;
            task.ActivityDate=System.Today().addDays(7);  
            taskSet.add(recUsage.Cookbook__c);
            taskList.add(task);     
           }
                
        }
        insert taskList;
   }
}

RecipeHandlerTrigger.cls

trigger RecipeHandlerTrigger on Recipe__c (before insert, before update,after insert, after update)
{
    //new RecipeTriggerHandler().run();  // Not Working, getting null pointer error on handler class

    if(Trigger.isBefore)
    {
        if(trigger.isInsert)
        {
            RecipeHandlerClass.checkRecipeInformation(Trigger.New);
            RecipeHandlerClass.complexityRate(Trigger.New);
        }
        if(Trigger.isUpdate) 
        {
            RecipeHandlerClass.checkRecipeInformation(Trigger.New);
            RecipeHandlerClass.complexityRate(Trigger.New);
        }         
    }

    if(Trigger.isAfter)
    {
        if(trigger.isInsert)
        {
            
        }
        if(Trigger.isUpdate) 
        {
            RecipeHandlerClass.createReviewTask(Trigger.New);  

        }         
    }

}