I am using JSONDecoder() in Swift and need to get better error messages.
Within the debug description (for example) I can see messages like "The given data was not valid JSON", but I need to know it is that rather than a network error (for example).
let decoder = JSONDecoder()
if let data = data{
do {
// process data
} catch let error {
// can access error.localizedDescription but seemingly nothing else
}
I tried to cast to a DecodingError, but this does not seem to reveal more information. I certainly don't need the string - even an error code is much more helpful than this...
Never print error.localizedDescription in a decoding catch block. This returns a quite meaningless generic error message. Print always the error instance. Then you get the desired information.
let decoder = JSONDecoder()
if let data = data {
do {
// process data
} catch {
print(error)
}
Or for the full set of errors use
let decoder = JSONDecoder()
if let data = data {
do {
// process data
} catch let DecodingError.dataCorrupted(context) {
print(context)
} catch let DecodingError.keyNotFound(key, context) {
print("Key '\(key)' not found:", context.debugDescription)
print("codingPath:", context.codingPath)
} catch let DecodingError.valueNotFound(value, context) {
print("Value '\(value)' not found:", context.debugDescription)
print("codingPath:", context.codingPath)
} catch let DecodingError.typeMismatch(type, context) {
print("Type '\(type)' mismatch:", context.debugDescription)
print("codingPath:", context.codingPath)
} catch {
print("error: ", error)
}