Parsing unknown number of items in SWIFT / SWIFT UI - json

Question

im working on a project in SwiftUI and I am new to Parsing JSON.
I have the following JSON file:
{
"index": "001",
"name": "Joe",
"courses": {
"course_1": "English",
"course_2": "CS",
"course_3": "Maths"
},
"count": 3
}
My problem is that not every student has the same number of courses. How could I fetch courses without knowing how many there are ?
My struct:
struct Student: Decodable {
var index: String
var name: String
var courses: [Course]
var count: Int
struct Course {
}
}

Answer 1

You can also model the struct Student like so,
struct Student: Decodable {
var index: String
var name: String
var courses: [String:String]
var count: Int
}
In the above code, I've used [String:String] type for courses instead of [Course].

Answer 2

You can do some custom decoding:
struct Student : Decodable {
let index: String
let name: String
let courses: [String]
enum CodingKeys: CodingKey {
case index
case name
case count
case courses
}
struct CourseCodingKeys: CodingKey {
var stringValue: String
init?(stringValue: String) {
self.stringValue = stringValue
}
var intValue: Int?
init?(intValue: Int) {
// this creates a key such s "course_1" using an integer
self.stringValue = "course_\(intValue)"
}
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
// decode the simple properties
index = try container.decode(String.self, forKey: .index)
name = try container.decode(String.self, forKey: .name)
// get the count
let courseCount = try container.decode(Int.self, forKey: .count)
// get the object that has the courses
let nestedContainer = try container.nestedContainer(keyedBy: CourseCodingKeys.self, forKey: .courses)
if courseCount == 0 {
courses = []
} else {
// for 1 to courseCount, decode a string for that key
courses = try (1...courseCount)
.map { try nestedContainer.decode(String.self, forKey: CourseCodingKeys.init(intValue: $0)!) }
}
}
}
Usage:
// ["English", "CS", "Maths"]
try jsonDecoder.decode(Student.self, from: data).courses