SwiftyDropbox - how to catch improperly formatted path

Question

If I make a call, (e.g. using listFolder), and I pass in an invalid path argument, (e.g. no leading slash), I get the following error:

precondition failed: "Does not exist must match pattern "\A(?:(/(.|[
])*)?|id:.*|(ns:[0-9]+(/.*)?))\z":

I understand why the error occurs, but the error seems to occur, before the call gets made, and doesn't show up, when I check the response for an error. My question is, how can I catch this kind of error of the path argument?

Thanks

Greg-DB · Accepted Answer

The SDK has a copy of the API specification and can tell when the supplied value isn't valid without making a call to the server (and thus without going through the API error callback).

You'll need to prevent your app from using invalid values like this in the first place. E.g., only use safe values returned by the API, such as in Metadata.pathLower, or just "" for root. If your app allows the user to manually enter in path values, you'll need to check them against the pattern in that error message first.