Trigger Problems

1. Create two fields on Account object a. Number of Open Tasks b. Number of Closed Tasks. Write a trigger on Task object, that will update the value of Number of Open tasks and Number of Closed Tasks field on its related Account.
   We'll be solving this trigger problem in two ways
   Solution 1:
   Trigger Code

   
       trigger CountTaskTrigger on Task (after insert, after update, after delete) {
       if(trigger.isInsert){
           CountTaskTriggerHandler.countTasks(Trigger.New);
       }
       if(trigger.isUpdate){
           CountTaskTriggerHandler.countTasks(Trigger.New, Trigger.oldMap);
       }
       if(trigger.isDelete){
           CountTaskTriggerHandler.countTasks(Trigger.old);
       }
   	}
       

   Handler Code

   
       public class CountTaskTriggerHandler {
       public static void countTasks(List<Task> tasks){
           Set<Id> accountIdSet = new Set<Id>();
           
           for(Task task :tasks){
               if(task.WhatId != null){
                   accountIdSet.add(task.WhatId);
               }
           }
           if(accountIdSet.size() > 0){
               commonMethod(accountIdSet);
           }
       }
       public static void countTasks(List<Task> newTasks, Map<Id, Task> oldTasksMap){
           Set<Id> accountIdSet = new Set<Id>();
           
           for(Task task: newTasks){
               if(oldTasksMap.get(task.Id).WhatId != task.WhatId){
                   accountIdSet.add(oldTasksMap.get(task.Id).WhatId);
               }
               accountIdSet.add(task.WhatId);
           }
           if(accountIdSet.size() > 0){
               commonMethod(accountIdSet);
           }
       }
       private static void commonMethod(Set<Id> accountIdSet){        
           
           Map<String, String> openTasksMap = new Map<String, String>();
           Map<String, String> closedTasksMap = new Map<String, String>();
           List<Account> accountList = new List<Account>();
           
           for(AggregateResult aggRes: [SELECT WhatId, count(id) totalTask FROM Task WHERE Status = 'Not Started' GROUP BY WhatId]){
               openTasksMap.put(String.valueOf(aggRes.get('WhatId')), String.valueOf(aggRes.get('totalTask')));
           }
           
           for(AggregateResult aggRes: [SELECT WhatId, count(id) totalTasks FROM Task WHERE Status = 'Completed' GROUP BY WhatId]){
               closedTasksMap.put(String.valueOf(aggRes.get('WhatId')), String.valueOf(aggRes.get('totalTasks')));
           }
           
           for(Account account: [SELECT Id, Numbe_of_Open_Tasks__c, Number_of_Closed_Tasks__c FROM Account WHERE Id IN: accountIdSet]){
               if(openTasksMap.containsKey(account.Id)){
                   account.Numbe_of_Open_Tasks__c = String.valueOf(openTasksMap.get(account.Id));
               }else {
                   account.Numbe_of_Open_Tasks__c = '0';
               }
               if(closedTasksMap.containsKey(account.Id)){
                   account.Number_of_Closed_Tasks__c = String.valueOf(closedTasksMap.get(account.Id));
               }else {
                   account.Number_of_Closed_Tasks__c = '0';
               }
               accountList.add(account);
           }
           
           if(accountList.size() > 0){
               update accountList;
           }
       }
   }
       

   
   Solution 2:
   Trigger Code

   
       trigger CountTaskTrigger on Task (after insert, after update, after delete) {
       if(trigger.isInsert){
           CountTaskTriggerHandler.countTasks(Trigger.New);
       }
       if(trigger.isUpdate){
           CountTaskTriggerHandler.countTasks(Trigger.New, Trigger.oldMap);
       }
       if(trigger.isDelete){
           CountTaskTriggerHandler.countTasks(Trigger.old);
       }
   	}
       

   Handler Code

   
       public class CountTaskTriggerHandler {
       public static void countTasks(List<Task> tasks){
           Set<Id> accountIdSet = new Set<Id>();
           
           for(Task task :tasks){
               if(task.WhatId != null){
                   accountIdSet.add(task.WhatId);
               }
           }
           if(accountIdSet.size() > 0){
               commonMethod(accountIdSet);
           }
       }
       public static void countTasks(List<Task> newTasks, Map<Id, Task> oldTasksMap){
           Set<Id> accountIdSet = new Set<Id>();
           
           for(Task task: newTasks){
               if(oldTasksMap.get(task.Id).WhatId != task.WhatId){
                   accountIdSet.add(oldTasksMap.get(task.Id).WhatId);
               }
               accountIdSet.add(task.WhatId);
           }
           if(accountIdSet.size() > 0){
               commonMethod(accountIdSet);
           }
       }
       private static void commonMethod(Set<Id> accountIdSet){
           
        Map<Id, List<Task>> openTasksMap = new Map<Id, List<Task>>();
           Map<Id, List<Task>> closedTasksMap = new Map<Id, List<Task>>();
           
           List<Account> accountList = new List<Account>();
           
           for(Task task : [SELECT id, WhatId, Status FROM Task WHERE WhatId IN : accountIdSet]){
               if(task.Status == 'Not Started'){
                   if(openTasksMap.containsKey(task.WhatId)){
                       List<Task> localTaskList = openTasksMap.get(task.WhatId);
                       localTaskList.add(task);
                       openTasksMap.put(task.WhatId, localTaskList);
                   }else {
                       openTasksMap.put(task.WhatId, new List<Task>{task});
                   }
               }else if(task.Status == 'Completed'){
                   if(closedTasksMap.containsKey(task.WhatId)){
                       List<Task> localTaskList = closedTasksMap.get(task.WhatId);
                       localTaskList.add(task);
                       closedTasksMap.put(task.WhatId, localTaskList);
                   }else {
                       closedTasksMap.put(task.WhatId, new List<Task>{task});
                   }
               }
           }
           for(Account account: [SELECT Id, Numbe_of_Open_Tasks__c, Number_of_Closed_Tasks__c FROM Account WHERE Id IN: accountIdSet]){
               if(openTasksMap.containsKey(account.Id)){
                   account.Numbe_of_Open_Tasks__c = String.valueOf(openTasksMap.get(account.Id).size());
               }else {
                   account.Numbe_of_Open_Tasks__c = '0';
               }
               if(closedTasksMap.containsKey(account.Id)){
                   account.Number_of_Closed_Tasks__c = String.valueOf(closedTasksMap.get(account.Id).size());
               }else {
                   account.Number_of_Closed_Tasks__c = '0';
               }
               accountList.add(account);
           }
           if(accountList.size() > 0){
               update accountList;
           }              
       }
   }
       

   Guys Please comment below if you like this or if you have any question. I'll be happy to help. Thanks!

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