         if !aObj.uid {
             // only NEW object have a nil uid
             
-            var pos  = self.register()
+            var pos  = self.registerBlock()
             result = self.calculateID(pos)
             aObj.uid = result
             

        
        if aObj.uid {
            self.cache.removeObjectForKey(aObj.uid!)
            self.deleteData(aObj.uid!)
            aObj.uid = nil;
        }
    }

    
    func addObject(aObj: O) -> UID {
        
        var pos = registerBlock()
        var uid = calculateID(pos)
    
        self.writeBlock(aObj.data, atPos: pos)
        
        aObj.uid = uid
        aObj.dirty = false
