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Vijay@sfdcVijay@sfdc 

Write program using map

Hello ,
can any one help me  write below code using Map. i am really not understanding how to plan program in map , can any one help me how to plan program in map instead of lists, i have aware of all map functions,
your help  is appreciable

trigger AccountInsert on Account (before insert,before update) {
  for(account acc:trigger.new)
    {
        list<account> myaccount =[select id, name from account where name=:acc.name];
        if(myaccount.size() >0 )
        {
            acc.name.adderror('account name already existed');
           acc.adderror('account name already existed!!!');
        }
    }
/*
    //using map
    list<account> acclist= new list<account>();
    map<id,name> Mapofnames= new map<id,name>();
    */
    
   
}
 
Best Answer chosen by Vijay@sfdc
Nayana KNayana K
trigger AccountTrigger on Account (before insert, before update)
{
    AccountTriggerHandler objAccountHandler = new AccountTriggerHandler();
    if(Trigger.isBefore && Trigger.isInsert)
        objAccountHandler.onBeforeInsert(Trigger.New);
    else if(Trigger.isBefore && Trigger.isUpdate)
        objAccountHandler.onBeforeUpdate(Trigger.oldMap, Trigger.NewMap);

}


public with sharing class AccountTriggerHandler
{
    public AccountTriggerHandler()
    {
    }

    public void onBeforeInsert(List<Account> lstNewAccount)
    {
        
        preventDuplicates(new Map<Id,Account>(), lstNewAccount);
        
    }
    
    public void onBeforeUpdate(Map<Id,Account> mapOldAccount, Map<Id,Account> mapNewAccount)
    {
        
        preventDuplicates(mapOldAccount, mapNewAccount.values());
        
    }
    
    private void preventDuplicates(Map<Id,Account> mapOldAccount, List<Account> lstNewAccount)
    {
        Map<String,Account> mapStrNameToAccount = new Map<String,Account>();
        
        // Collect All Names from Trigger.New
        for(Account objAccount : lstNewAccount)
        {
            /* 1. On insert
            OR
            2. On update but only if Name is changed
            
            */
            if(Trigger.isInsert || (Trigger.isUpdate && mapOldAccount.get(objAccount.Id).Name != objAccount.Name))
                mapStrNameToAccount.put(objAccount.Name, objAccount);
        }
            
        
        // iterate over matching Account and add error
        for(Account objMatchingAccount : [SELECT Id,Name
                                         FROM Account
                                         WHERE Name IN:mapStrNameToAccount.keySet()])
        {
            mapStrNameToAccount.get(objMatchingAccount.Name).Name.addError('Record already exists with same name!');
        }
    }
}

All Answers

Nayana KNayana K
trigger AccountTrigger on Account (before insert, before update)
{
    AccountTriggerHandler objAccountHandler = new AccountTriggerHandler();
    if(Trigger.isBefore && Trigger.isInsert)
        objAccountHandler.onBeforeInsert(Trigger.New);
    else if(Trigger.isBefore && Trigger.isUpdate)
        objAccountHandler.onBeforeUpdate(Trigger.oldMap, Trigger.NewMap);

}


public with sharing class AccountTriggerHandler
{
    public AccountTriggerHandler()
    {
    }

    public void onBeforeInsert(List<Account> lstNewAccount)
    {
        
        preventDuplicates(new Map<Id,Account>(), lstNewAccount);
        
    }
    
    public void onBeforeUpdate(Map<Id,Account> mapOldAccount, Map<Id,Account> mapNewAccount)
    {
        
        preventDuplicates(mapOldAccount, mapNewAccount.values());
        
    }
    
    private void preventDuplicates(Map<Id,Account> mapOldAccount, List<Account> lstNewAccount)
    {
        Map<String,Account> mapStrNameToAccount = new Map<String,Account>();
        
        // Collect All Names from Trigger.New
        for(Account objAccount : lstNewAccount)
        {
            /* 1. On insert
            OR
            2. On update but only if Name is changed
            
            */
            if(Trigger.isInsert || (Trigger.isUpdate && mapOldAccount.get(objAccount.Id).Name != objAccount.Name))
                mapStrNameToAccount.put(objAccount.Name, objAccount);
        }
            
        
        // iterate over matching Account and add error
        for(Account objMatchingAccount : [SELECT Id,Name
                                         FROM Account
                                         WHERE Name IN:mapStrNameToAccount.keySet()])
        {
            mapStrNameToAccount.get(objMatchingAccount.Name).Name.addError('Record already exists with same name!');
        }
    }
}
This was selected as the best answer
Amit Chaudhary 8Amit Chaudhary 8
Please try below code
trigger AccountInsert on Account (before insert,before update) 
{
	Set<Id> setAccID = new Set<ID>();
	Set<Id> setAccName = new Set<ID>();

	for(account acc: trigger.new )
    {
		setAccName.add(acc.Name);
		setAccID.add(acc.id);
	}
	
	List<Account> lstAccount = [ select id, name from account where name=:setAccName and id not in :setAccID ] ;

	Map<String,Account> MapAccount = new Map<String,Account>();
	For(Account acc : lstAccount )
	{
		MapAccount.put(acc.name,acc);
	}
	
	for(account acc: trigger.new )
    {
        if( MapAccount.containsKey(acc.name) )
        {
            acc.name.adderror('account name already existed');
        }
    }

}
Let us know if this will help you

 
Vijay@sfdcVijay@sfdc
Thanks Amit,
@Nayana K your explanation is awesome, with great best practices, its helped me lot for next level , your work is appreciable 
 
Vijay@sfdcVijay@sfdc
Hello Amit,

executing your code, i am getting bellow error
 Error: Invalid Data.
Review all error messages below to correct your data.
Apex trigger AccountInsertUsingMAP caused an unexpected exception, contact your administrator: AccountInsertUsingMAP: execution of AfterUpdate caused by: System.StringException: Invalid id: Duplicate test: External entry point
 
Amit Chaudhary 8Amit Chaudhary 8
It look like some issue is coming in your "AccountInsertUsingMAP " trigger. Please post code so that we can help you


1) http://amitsalesforce.blogspot.in/2015/06/trigger-best-practices-sample-trigger.html

Trigger Best Practices | Sample Trigger Example | Implementing Trigger Framework

1) One Trigger Per Object
A single Apex Trigger is all you need for one particular object. If you develop multiple Triggers for a single object, you have no way of controlling the order of execution if those Triggers can run in the same contexts

2) Logic-less Triggers
If you write methods in your Triggers, those can’t be exposed for test purposes. You also can’t expose logic to be re-used anywhere else in your org. 

3) Context-Specific Handler Methods
Create context-specific handler methods in Trigger handlers

4) Bulkify your Code
Bulkifying Apex code refers to the concept of making sure the code properly handles more than one record at a time.

5) Avoid SOQL Queries or DML statements inside FOR Loops
An individual Apex request gets a maximum of 100 SOQL queries before exceeding that governor limit. So if this trigger is invoked by a batch of more than 100 Account records, the governor limit will throw a runtime exception

6) Using Collections, Streamlining Queries, and Efficient For Loops
It is important to use Apex Collections to efficiently query data and store the data in memory. A combination of using collections and streamlining SOQL queries can substantially help writing efficient Apex code and avoid governor limits

7) Querying Large Data Sets
The total number of records that can be returned by SOQL queries in a request is 50,000. If returning a large set of queries causes you to exceed your heap limit, then a SOQL query for loop must be used instead. It can process multiple batches of records through the use of internal calls to query and queryMore

8) Use @future Appropriately
It is critical to write your Apex code to efficiently handle bulk or many records at a time. This is also true for asynchronous Apex methods (those annotated with the @future keyword). The differences between synchronous and asynchronous Apex can be found

9) Avoid Hardcoding IDs
When deploying Apex code between sandbox and production environments, or installing Force.com AppExchange packages, it is essential to avoid hardcoding IDs in the Apex code. By doing so, if the record IDs change between environments, the logic can dynamically identify the proper data to operate against and not fail

 
Vijay@sfdcVijay@sfdc
Same code , which i selected for best Anwer Amit :)
Srujana D 7Srujana D 7
trigger PreventDuplicateName on Student__c (before insert,before update,after update) {
map<string,Student__c> mapnewdata = new map<string,Student__c>();
//set<string> sname = new set<String>();
    if(trigger.isBefore&&trigger.isInsert){
        for(Student__c s : trigger.new){
           mapnewdata.put(s.Name,s);
        }
    }
    if(trigger.isBefore&&trigger.isUpdate){
        for(Student__c s : trigger.new){
           mapnewdata.put(s.Name,s);
        }
    }
    List<Student__c> stddata = [select name from Student__c where Name in:mapnewdata.keySet()];
    for(Student__c  std : trigger.new){
    if(stddata.size() > 0){
    std.Name.addError('Name already existed');
    }
   
}}