Under what circumstances does JSONSerialization.data(withJSONObject:) throw a catchable error?
Turns out it’s the same situation as this question: you can create a Swift string that contains invalid unicode (what?!), and that causes an exception.
let bogusStr = String( bytes: [0xD8, 0x00] as [UInt8], encoding: String.Encoding.utf16BigEndian)!do { let rawBody = try JSONSerialization.data( withJSONObject: ["foo": bogusStr], options: []) }catch { // Exception lands us here print("Caught error:", error) }Why does the example code in the original question crash, then, instead of also throwing an error?
Replying to a bug report, Apple informed me that you should call JSONSerialization.isValidJSONObject(_:) before data(withJSONObject:) if you don’t know for sure that the object is encodable, failing to do that is a misuse of the API, and that’s why they decided it should crash instead of throwing something catchable.