JSONSerializer.swift

import Foundation
import RealmSwift

class JSONSerializer {
    func serialize(input sourceName: String) {
        let path = Bundle.main.path(forResource: sourceName, ofType: nil)
        let url = URL(fileURLWithPath: path!)
        let jsonDecoder = JSONDecoder()
        do {
            let data = try Data(contentsOf: url)
            let json = try JSONSerialization.jsonObject(with: data, options: .allowFragments)
            guard json is [AnyObject] else {
                assert(false, "failed to parse")
                return
            }
            do {
                switch sourceName {
                case "Cats":
                    let cats = try jsonDecoder.decode([Cat].self, from: data)
                    let realm = try! Realm()
                    for cat in cats {
                        try! realm.write {
                            realm.add(cat)
                        }
                    }
                default:
                    let catPeople = try jsonDecoder.decode([CatPerson].self, from: data)
                    let realm = try! Realm()
                    for catPerson in catPeople {
                        try! realm.write {
                            realm.add(catPerson)
                        }
                    }
                }
            } catch {
                print("failed to convert data")
            }
        } catch let error {
            print(error)
        }
    }
}