How to avoid 'for' within a 'for' loop in sales force Trigger

Question

Create a custom field called “Number of Locations” (its API name: NumberofLocations__c) on the Account Object (Data Type=Number).Create multiple contacts by Account depending on the NumberofLocations__c field.

Trigger

trigger ContactsCreation on Account (after insert) {
    list<contact> listContact = new list<contact>();
    map<id,decimal> mapAcc=new map<id,decimal>();
    for(Account acc:trigger.new){
        mapAcc.put(acc.id,acc.NumberofLocations__c);
    }
    if(mapAcc.size()>0 && mapAcc!=null){
        for(Id accId:mapAcc.keyset()){
            for(integer i=0;i<mapAcc.get(accId);i++){
                contact newContact=new contact();
                newContact.accountid=accId;
                newContact.lastname='contact'+i;
                listContact.add(newContact);
            }
        }
    }
    if(listContact.size()>0 && listContact!=null)
        insert listContact;
}

Answer 1

No, you cannot generate a list of child Contact records without a for loop. You can, however, simplify testing and maintenance by breaking out a few of these methods into a Service Layer.

A few notes:

• You should add error handling to any cross-object DML in your triggers.
• There's no need to check if the list is empty.
• It is faster to set all fields at time of SObject construction by passing in name=value pairs.

Service Layer

More atomic build methods:

public static List<Contact> buildLocations(List<Account> records)
{
    List<Contact> locations = new List<Contact>();

    for (Account record : records)
        locations.addAll(buildLocations(record.Id, record.NumberOfLocations__c);
        // this way you only have to unit test one loop at a time
    
    return locations;
}
public static List<Contact> buildLocations(Id accountId, Integer count)
{
    List<Contact> locations = new List<Contact>();
    
    for (Integer i = 0; i < count; i++)
        locations.add(new Contact(AccountId=accountId, LastName='Contact' + i));
        // faster construction
    
    return locations;
}

Error handling:

public static void safeInsertLocations(List<Contact> locations, Map<Id, Account> parents);
{
    if (locations == null) return;
    // this strategy is called a "guard clause"
    // you don't have to guard against an empty list though

    try
    {
        insert locations;
    }
    catch (DmlException d)
    {
        for (Integer i = 0; i < d.getNumDml(); i++)
        {
            Account parent = parents.get(locations[i].AccountId);
            parent.addError(d);
        }
        // this is a pretty standard approach
        // for mapping errors back to parent records
    }
}

Answer 2

You can iterate on the accId as you've already set it up and just add 1 to an integer variable that you set up at before the beginning of the loop. Change your code as follows:

trigger ContactsCreation on Account (after insert) {
    list<contact> listContact = new list<contact>();
    map<id,decimal> mapAcc=new map<id,decimal>();
    for(Account acc:trigger.new){
        mapAcc.put(acc.id,acc.NumberofLocations__c);
    }
    if(mapAcc.size()>0 && mapAcc!=null){
        integer i = 0;
        for(Id accId:mapAcc.keyset()){                
            contact newContact=new contact();
            newContact.accountid=accId;
            newContact.lastname='contact'+i;
            listContact.add(newContact);
            integer i++;           
        }
    }
    // if(listContact.size()>0 && listContact!=null)
    // No need to test for size() or null
        insert listContact;
}

That having been said, it's unclear to me what you intended to do with your map to begin with. Unless you've omitted part of your code, the map serves no purpose for the code in your trigger as the number of locations isn't used. Did you intend to nest the location number within a for loop to further sort your contacts or add this information to the contact perhaps?