Enum with associated values

example.swift

//: Playground - noun: a place where people can play

import UIKit

struct Category1: Decodable {
    let recordID          : String?
    let Year_when_Started : String?
    let Problem_Name      : String?
}

struct Category2: Decodable {
    let Refused     : String?
    let Date_Given  : String?
    let recordID    : String?
    let Date_when_Next_Due : String?
}

struct Category3: Decodable {
    var Address       : String?
    var City          : String?
    var Date_of_Birth : String?
    var First_Name    : String?
    var Gender        : String?
    var Last_Name     : String?
    var Postal_Code   : String?
    var recordID      : String?
}

enum Category {
    
    case category1([Category1])
    case category2([Category2])
    case category3([Category3])
    
    var url: String {
        switch self {
        case .category1(_): return "Category1"
        case .category2(_): return "Category2"
        case .category3(_): return "Category3"
        }
    }
}

// CHANGE THIS TO EITHER: .category1, .category2, .category3
let mainCategory: Category = .category1([])

extension Category: Decodable {
    
    init(from decoder: Decoder) throws {
        switch(mainCategory) {
        case .category1(_):
            self = try .category1(decoder.singleValueContainer().decode([Category1].self))
        case .category2(_):
            self = try .category2(decoder.singleValueContainer().decode([Category2].self))
        case .category3(_):
            self = try .category3(decoder.singleValueContainer().decode([Category3].self))
        }
    }
}

// CHOOSE EITHER EXAMPLE OF THESE JSON TO MATCH THE CATEGORY:
 // Example: JSON Category1
let json1 = """
[
{"recordID": "111"},
{"recordID": "222", "Year_when_Started" : "2000"},
{"recordID": "333", "Year_when_Started" : "2011", "Problem_Name" : "Problem1"}
]
""".data(using: .utf8)!

// // Example: JSON Category2
//let json1 = """
//[
//{"Refused": "refused1"},
//{"Refused": "refused2", "Date_Given": "2017", "recordID": "record4"},
//{"Refused": "refused3", "recordID": "record4", "Date_when_Next_Due": "2018"}
//]
//""".data(using: .utf8)!

// // Example: JSON Category3
//let json1 = """
//[
//{"Address": "address1", "City" : "city1", "First_Name" : "Name1"},
//{"Address": "address2", "City" : "city2", "First_Name" : "Name2", "Last_Name": "LastName2"},
//{"Address": "address3", "City" : "city3", "First_Name" : "Name3", "Last_Name": "LastName3", "Postal_Code": "code3"},
//]
//""".data(using: .utf8)!

let data1 = try JSONDecoder().decode(Category.self, from: json1)
print(data1)