How to use an init(from decoder:) when reading bundled JSON data - json

Question

I have have a JSON dictionary array and need to decode it to make a data type (Hitter), the Hitter object needs to hold the raw JSON data and I need to add properties to the Hitter throughout the life of the app. I've discovered I need to use init(from decoder:) but how do I call the init properly...I will be storing the Hitter in the League struct.
struct League {
var Hitters: Set<Hitter>
func loadHitters() {
...//ingest json from bundle,
//store decoded Hitter objects in temp array,
//then append each item from temp array into League.Hitters set.
}
}
To be clear, my Hitter struct already has the init set up, I need help using the decoder from this point.
EDIT:
I've discovered the solution and it requires the use of retrieving the JSON keys and linking them to your CodingKeys enum. Here's my shortened Hitter class:
struct Hitter: Player, Decodable {
//partial list of properties in JSON data
let strPos: String
let OBP: Float
let wRAA: Float //weightedRunsAboveAverage
//partial list of properties in JSON data - end
//partial list of additional properties
var valAboveReplacement: Float = 0.0
var wOBP: Float {
return OBP * Float(PA)
}
//partial list of additional properties - end
}
I declare the CodingKeys and init(decoder:) in an extension for compartmentalization's sake
extension Hitter {
enum CodingKeys: String, CodingKey {
case strPos, OBP, wRAA
}
convenience init(from decoder: Decoder) {
//container links all the CodingKeys and JSONDecoder keys for proper referencing. Returns the data stored in this decoder as represented in a container keyed by the given key type
let container = try decoder.container(keyedBy: CodingKeys.self)
let strPos = try container.decode(String.self, forKey: .strPos)
let OBP = try container.decode(Float.self, forKey: .OBP)
let wRAA = try container.decode(Float.self, forKey: .wRAA)
//pass my decoded values via a standard initializer
self.init(strPos: strPos, OBP: OBP, wRAA: wRAA)
}
}
This seems to work perfectly fine so long as I explicitly link the JSON format and the CodingKeys via a container.

Answer 1

If you design a struct, you get an memberwise initializer for free — assuming you don't define others initializers yourself But Struct auto inititializers are internal. You have to generate memeberwise initializer when you writing a module to make it public
"Default Memberwise Initializers for Structure Types The default
memberwise initializer for a structure type is considered private if
any of the structure’s stored properties are private. Otherwise, the
initializer has an access level of internal.
As with the default initializer above, if you want a public structure
type to be initializable with a memberwise initializer when used in
another module, you must provide a public memberwise initializer
yourself as part of the type’s definition."
Swift Docs "Swift Programming Language"