Core Data to-one/to-many relationship setting error?

FROM : Chataka
DATE : Sun Feb 24 11:39:39 2008

Hello,

I have a trouble with my non-document-based Core Data application and
hope some advice.

My app has a "Transaction" entity and it has a mainTransaction and a 
subTransactions
relationships which are set inverse each other.

mainTransaction to subTransactions is a to-many relationship, while
subTransactions to mainTransaction is a to-one relationship.

I have a method to create a main transaction and sub-transactions
like below.

- (void) createAndSetMainTransaction: (NSArray *) myDataArray  // 
array of myData
{
   MyDataType * myData;    // contains transaction attribute data to be 
filled in transactionMO
   NSManagedObject * firstTransactionMO = nil;    // a transactionMO which 
will be created first

   for ( myData in myDataArray )
   {
       NSManagedObject * transactionMO = [self 
createATransactionMOAndFillMyData: myData];

       if ( firstTransactionMO == nil )
       {
           firstTransactionMO = transactionMO;
       }
       else
       {
           [transactionMO setValue: firstTransactionMO forKey: 
@"mainTransaction"];  // problematic line
           //  setting the first transactionMO as the mainTransaction for all 
the
           // rest of the transactionMOs created within this method
       }
   }
}

-----

This method works and transactions created here are displayed in an 
NSTableView
through NSArrayController and Cocoa Bindings, exactly as I expected.

But once I save the data to a file (with NSSQLiteStoreType) and start 
the app again,
the app crashes when the app tries to display the data in the 
NSTableView.

If I commented out the "problematic line", the app doesn't crash and 
everything
seems fine except the subTransactions don't have the mainTransaction.

I don't figure out what is wrong with the problematic line and hope some
advice to fix this problem.

Thank you.