How do I set the record ID for a DBRecord when it's created on iOS?

I need to set the ID of a DBRecord (Dropbox record) when I create it, but I don't see in the documentation where it explains how. It just says, "Each record has a string ID. An ID can be provided when a record is created, or one will be automatically generated and assigned if none is provided. Once a record is created, the ID cannot be changed."

I've tried the following...

NSString *id = @"1";
NSDictionary *record = @{@"recordId" : id, @"otherField" : @"whatever"};
[tbl insert:record];
[self.datastore sync:nil]; 

...but I'm completely guessing at the name of the id field and that code just creates an additional property called "recordId", rather than setting the actual record id.

How do I set the id for a DBRecord when I create it? Thanks in advance for your wisdom!