Sample code snippet to read local JSON file in iOS10 and iOS 11

reading_local_json_file.swift

if let resource = Bundle.main.url(forResource: "US zip (postal) codes", withExtension: "json"),
   let postalCodesData = try? Data(contentsOf: resource, options: Data.ReadingOptions.alwaysMapped){
       do{
             let decodedObject = try JSONDecoder().decode(PostalCodeResponse.self, from: postalCodesData)
             DispatchQueue.main.async { [weak self] in
                // update UI
             }
       }catch let parsingError {
             print(parsingError)
       }
   }



//helpers
struct PostalCode: Codable {
    var city: String
    var loc: [Double]
    var pop: Int
    var state: String
    var _id: String
}


struct PostalCodeResponse: Codable {
    var codes: [PostalCode]
}