Map Described

I have recently begun to understand the value of Maps when writing Apex triggers and classes, they can be very powerful. The most common Map used is the 'Map <ID, sObject>' this means that the Key of the Map is the ID and the value is the object related to the ID.

Typically you will see it initiated in this way:

Map<ID,sObject> sObMap = new Map<ID,sObject>([SELECT *fields* FROM sObject WHERE *conditions*]);

This is how I used it in a recent bit of code I wrote. This trigger copies the owner of the Account related to a case down to the case record on a custom field.




trigger CaseBeforeInsertTrigger on Case (before insert) {

    Set<Id> accountIds = new Set<Id>(); //set to hold list of Accounts

    for (Case c : Trigger.new) { //loop through all cases and pull the Account ID into the set above
        if(c.AccountId != null) {
        accountIds.add(c.AccountId);
        }      
    }
 
    Map<ID, Account> acct = new Map<ID, Account>([select id, ownerid from Account where id = : AccountIds]); //create a map where the ID is the Key and the Value is the sObject (Account)

    if(acct.size() > 0) {
        for(Case c: Trigger.new) { //if there are values in the map, loop through the new cases
      if (c.AccountId != null){
     
          Account acctUpdate= acct.get(c.AccountID); //look back into the map and using the Account ID grab the Account sObject
          c.Account_Owner__c = acctUpdate.OwnerId;
     
      }
        }
    }
}