All About Trigger Handler & Helper in #Salesforce #ApexTrigger

AccountTrigger.java

trigger AccountTrigger on Account (before delete) {
    if ( Trigger.IsBefore && Trigger.isDelete ) {
        AccountTriggerHandler.handleBeforeDelete( Trigger.Old, Trigger.oldMap );
    }
}

AccountTriggerHandler.java

public class AccountTriggerHandler {

    public static void handleBeforeDelete(List<Account> oldAccountList, Map<Id, Account> oldAccountMap) {
        /*
     * AccountTrigger => Handler AccountTriggerHandler
     * 
     */ 
	/*
	 * Trigger.old => List<sObject> => List<Account>
	 * Trigger.oldMap => Map<id, sobject> => Map<Id, Account>
	 * keySet() => Set<Keys> => Set<id> => Set<AccountId>
	 */ 
    Set<Id> accountIdsSet = oldAccountMap.keySet();
    List<Opportunity> opportunityList = [
        								 Select Id, Name, StageName, AccountId
                                         From Opportunity 
                                         Where AccountId IN : accountIdsSet
                                         AND IsWon = true
                                        ];
    Map<Id, Opportunity> opportunitiesMap = new Map<id,Opportunity>();
    // Key -> AccountId, Value -> Opportunity
    /* Approach 1 Using List 
        for (Account acc : oldAccountList) {
            for ( Opportunity opp : opportunityList) { 
                if ( acc.Id == opp.AccountId) {
                    acc.addError('You can not delete the Account which have Closed Won Opportunities! Please Contact your admin');
                }
            }
        }
	*/
    
    /* Approach 2 Usin Map */
        for ( Opportunity opp : opportunityList) { 
            if ( !opportunitiesMap.containsKey(opp.AccountId) ) {
                opportunitiesMap.put(opp.AccountId, opp);
            }
        }
        
        for (Account acc : oldAccountList) { 
            if( opportunitiesMap.containsKey(acc.Id) ) {
                acc.addError('You can not delete the Account which have Closed Won Opportunities! Please Contact your admin');
            }
        }
    }
}