Related List population in Apex

[notsosmart]

In an Apex batch process, I am s creating record of a new RecordType that is a consolidation of 2 existing RecordTypes of  each Account record.

It is functioning properly EXCEPT it's not getting the Related Lists.  I presume that it would require specific code to address it but,  for instance,  to populate the Related Contacts, I used:

Note - The item.Accounts is the source record List which includes Account.Contacts in the query,  myAccount is the new record being created.

myAccount.Contacts = item.Account.Contacts;     I got the error  -  field is not writable.

I tried     myAccount.Contacts.Id = 'xx';   -  ( xx is just to test the reference) which resulted in  the error  -   Invalid foreign key relationship.

Any ideas on how this would be populated?

[Jake Gmerek · Accepted solution]

So you are approaching it the wrong way, the contacts are related to the account not the other way around.  You need something like this:

for (contact c: item.Account.Contacts){

c.accountID = item.Account.ID;

}

update item.Account.Contacts

I am not sure what the structure of the item object is, so you may have to tweak that a little bit and i am not sure if you can do this "update item.Account.Contacts" you may have to push your contacts onto a separate list and update them that way, but this should get you started.