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Force.platformForce.platform 

map

Hello All,
            i am new to salesforce. i am not getting how to start with map and how to deal wirh map, wheen should use map and how to use map in apex. so please guide about map .
ashishashish
hi, 

Map is a collection of key-value pairs where each unique key maps to a single value,
here is an exapmle of triggers that updates a Contact Owner with the Account Owner before updating Account,
Account is a Lookup on Contact Object.


trigger accountowner on Account (before update) {
    map<id,id> mp=new map<id,id>();
    
    for(Account ac:Trigger.new){
        mp.put(ac.id,ac.OwnerId);    
    }
    
    list<contact> con=new list<Contact>();
    for(contact ac:[Select id,Ownerid,accountid from Contact where Accountid=:mp.keySet()]){
        con.add(new contact(id=ac.id,ownerid=mp.get(ac.accountid)));
    }
    update con;
}

thanks 
Ashish
Abhilash Mishra 13Abhilash Mishra 13

Hi,
map is very important in salesforce.many times you can use it to avoid unnecessary SOQL Queries saving governer limit.
like this query:
map<id,account> accountMap=new map<id,account>([select id,name from account]);
will store accounts data, with account id as key and Record as value. you can easily retrieve any account anywhere in code by usung map methods if you know account id.

For Map class read here: https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_methods_system_map.htm
 
Amit Chaudhary 8Amit Chaudhary 8
Please check below post for same
1) http://amitsalesforce.blogspot.com/2016/09/collection-in-salesforce-example-using.html

Map : A map is a collection of key-value pairs 
Each unique key maps to a single value. Keys can be any primitive data type, while values can be a primitive, sObject, collection type or an Apex object.

EX: Map<Id, Account> accMap = new Map<Id, Account>();

Map<Integer, String> mapOfString = new Map<Integer, String>(); mapOfString.put(1, 'Amit'); mapOfString.put(2, 'Rahul'); System.assert(mapOfString.containsKey(1)); 
String value = mapOfString.get(2); 
System.assertEquals('Rahul', value); Set<Integer> s = mapOfString.keySet();
Map<String, String> myMap = new Map<String, String>{'a' => 'b', 'c' => 'd'};

Example 1:-  Using trigger populate the Account Field on the Contact record (only insert scenario)

If we use List and not Map

Apex Class 
trigger ContactTriggerWithList on Contact (before insert) 
{
Set<Id> SetAccountId = new Set<Id>(); // Use set to collect unique account ID

for(Contact con: Trigger.new) 
{
 if(con.AccountId != null) 
 {
  SetAccountId.add(con.AccountId); // add Account in Set
 }
}

if( SetAccountId.size() >0 ) 
{
 List<Account> listAccount = [ Select Id, Name, Type from Account where Id IN :SetAccountId ]; // Query Related Account
 
 for(Contact con: Trigger.new) 
 {
  if(con.AccountId != null)
  {
   for(Account acc: listAccount)
   {
    if(con.AccountId == acc.Id)
    {
     con.Type__c = acc.Type;
    }
   }
  }
 }
} 
}
NOTE:- In this we are using List of Accounts, Where we have to loop through the matching Account every time to populate the Type__c in the second for loop. In this case need to use nested loop.
To Above the Nested Loop We can use the Map .

Same Trigger using the Map:
  
trigger ContactTriggerWithMap on Contact (before insert) 
{
    Set<Id> SetAccountId = new Set<Id>();
    for(Contact cont: Trigger.new) 
 {
        if(cont.AccountId != null) 
  {
            SetAccountId.add(cont.AccountId);
        }
    }
    
    if(SetAccountId.size() > 0 ) 
 {
        Map<Id, Account> mapAccount = new Map<Id, Account>([Select Id, Name, Type from Account where Id IN :SetAccountId ]);
        for(Contact cont: Trigger.new) 
  {
            if(cont.AccountId != null && mapAccount.containsKey(cont.AccountId) ) 
   {
                cont.Type__c = mapAccount.get(cont.AccountId).Type;
            }
        }
    }
}
NOTE:- Here we are using map of Account so we can directly use the Map to get the Account record. No need of 2nd for loop here