@clarkperkins Sorry, I deleted the other comments preemptively. I'm pretty sure `self.mappingDictionary[locationId]` gets replaced with `[self.mappingDictionary objectForKeyedSubscript:locationId]` at compile time, which returns `nil` if no value is associated with the key, rather than throwing an exception. In the [docs](https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSDictionary_Class/Reference/Reference.html#//apple_ref/occ/instm/NSDictionary/objectForKeyedSubscript:), it says `objectForKey:` behaves in the same way, so we should be fine leaving this as `self.mappingDictionary[locationId]`.