Swift JSON Decoder Error: Missing something - json

Question

I am using a JSON encoder and decoder to be able to save a custom object to my user defaults. The object I am trying to encode and decode is a Mapbox Directions Route Object (See their documentation here: Mapbox Route
I have successfully used a JSON Encoder and Decoder for many things in my app. But for some reason, I can't get it to work with the Route object. Following is my JSON Encoder:
//Encode route response Object to pass it to Defaults
do {
// Create JSON Encoder
let encoder = JSONEncoder()
// Encode Note
let encodedRoute = try encoder.encode(route)
// Write/Set Data
UserDefaults.standard.set(encodedRoute, forKey: "routeObject")
print("Encoded route Object.")
} catch {
print("Unable to Encode route (\(error))")
}
Note that the console prints "Encoded route Object.", which should mean it worked.
Following now is my Decoder, which does not work and throws me the error I added to the catch statement:
//Read/Get response Object
if let encodedRoute = UserDefaults.standard.data(forKey: "routeObject") {
do {
// Create JSON Decoder
let decoder = JSONDecoder()
// Decode Note
myRoute = try decoder.decode(MapboxDirections.Route.self, from: encodedRoute)
print("Successfully decoded route Object!")
} catch {
print("Unable to Decode route. Error: \(error)")
}
}
The error which I get is: "Unable to Decode route. Error: missingOptions". Since RouteOptions is part of the Route object, I am guessing that something went wrong while encoding or decoding, leading to a missing piece of the object. I tried encoding and decoding a RouteResponse (which contains multiple Routes), which returned me "missingCredentials". Again, Credentials is part of RouteResponse. What could I have done wrong? Both classes are working well otherwise and both already use many other Mapbox functions, so it cannot be something with the imports or such.
If there is a workaround to pass an object to another class without using getter and setters (which bugs also), I'd be happy to hear it.

Answer 1

It's a custom error thrown by the MapBox API.
From their code:
/**
An error that occurs when encoding or decoding a type defined by the MapboxDirections framework.
*/
public enum DirectionsCodingError: Error {
/**
Decoding this type requires the `Decoder.userInfo` dictionary to contain the `CodingUserInfoKey.options` key.
*/
case missingOptions
...
}
In Route, we can see the comments on init(from decoder:), which is, under the hood called by decoder.decode(_:from:):
/**
Initializes a route from a decoder.
- precondition: If the decoder is decoding JSON data from an API response, the `Decoder.userInfo` dictionary must contain a `RouteOptions` or `MatchOptions` object in the `CodingUserInfoKey.options` key. If it does not, a `DirectionsCodingError.missingOptions` error is thrown.
- parameter decoder: The decoder of JSON-formatted API response data or a previously encoded `Route` object.
*/
public required init(from decoder: Decoder) throws {
try super.init(from: decoder)
}
So you need to put, something like:
let decoder = JSONDecoder()
decoder.underInfo = [CodingUserInfoKey.options: someRouteOptions]
// or
decoder.underInfo = [CodingUserInfoKey.options: someMatchOptions]
I don't use that framework, but I guess that the usage on why which one to use should appear on their documentation or the git repo code. You can search maybe for RouteOptions/MatchOptions there.