Parse Complex Nested Data From server - ios

Question

I'm trying to parse data i've received from the server so as to display it into a UIPicker view. but it's too complex for me to parse and get it displayed into UIPIcker View. Whats the best way i can parse the following data into and make it ready for a UIPickerView.
This is the session trying to parse the information from the server
let url = NSURL(string: "http://dummy.com/api")!
let request = URLRequest(url: url as URL)
URLSession.shared.dataTask(with: request) { data, response, error in
if error == nil {
do {
let json = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers) as? NSDictionary
guard let parseJSON = json else{
print("Error While Parsing")
return
}
print(parseJSON)
let responseDic = parseJSON["response"] as? NSDictionary
let utilityCode = responseDic?["utility_code"] as? String
if utilityCode == "AFRICELL" {
let africellPackages = responseDic?["packages"] as! NSArray
print(africellPackages)
}
}catch{
return
}
}
}.resume()
The following data is the response from the server when the GET request is made.
{
"status": "OK",
"response": [
{
"utility_code": "AIRTEL",
"packages": [
{
"package_id": 33,
"package_name": "Daily 10MB",
"package_code": "6000",
"package_price": 300
},
{
"package_id": 34,
"package_name": "Daily 20MB",
"package_code": "6002",
"package_price": 500
},
{
"package_id": 65,
"package_name": "Weekly Roaming 200MB",
"package_code": "6030",
"package_price": 100000
}
]
},
{
"utility_code": "AFRICELL",
"packages": [
{
"package_id": 68,
"package_name": "Daily 10 MB",
"package_code": "5000",
"package_price": 290
}
]
},
{
"utility_code": "SMART",
"packages": [
{
"package_id": 69,
"package_name": "Daily 50 MB",
"package_code": "8000",
"package_price": 500
}
]
},
{
"utility_code": "SMILE",
"packages": [
{
"package_id": 70,
"package_name": "Smile 1GB",
"package_code": "7006",
"package_price": 32000
}
]
}
]
}
Cheers and thanks for the help!

Answer 1

All examples below are provided without error checking for brevity. For production code, you should handle errors properly.
Swift 3 without any external framework
Most of the work to decode JSON manually involves defining the data model:
struct JSONResponse {
var status: String
var response: [Utility]
init(jsonDict: [String: AnyObject]) {
self.status = jsonDict["status"] as! String
self.response = [Utility]()
let response = jsonDict["response"] as! [AnyObject]
for r in response.map({ $0 as! [String: AnyObject] }) {
let utility = Utility(jsonDict: r)
self.response.append(utility)
}
}
}
struct Utility {
var code: String
var packages: [Package]
init(jsonDict: [String: AnyObject]) {
self.code = jsonDict["utility_code"] as! String
self.packages = [Package]()
let packages = jsonDict["packages"] as! [AnyObject]
for p in packages.map({ $0 as! [String: AnyObject] }) {
let package = Package(jsonDict: p)
self.packages.append(package)
}
}
}
struct Package {
var id: Int
var name: String
var code: String
var price: Int
init(jsonDict: [String: AnyObject]) {
self.id = jsonDict["package_id"] as! Int
self.name = jsonDict["package_name"] as! String
self.code = jsonDict["package_code"] as! String
self.price = jsonDict["package_price"] as! Int
}
}
And how to use it:
let jsonDict = try! JSONSerialization.jsonObject(with: data) as! [String: AnyObject]
let jsonResponse = JSONResponse(jsonDict: jsonDict)
let utilities = jsonResponse.response
print(utilities)
Swift 3 with ObjectMapper
Decoding JSON is it of a pain in standard Swift. You need an external JSON framework like ObjectMapper to ease the pain in mapping between the JSON data and your data model. Install ObjectMapper from CocoaPod or Carthage.
First, define your data model in a separate file:
import ObjectMapper
struct JSONResponse : Mappable {
var status: String?
var response: [Utility]?
init?(map: Map) { }
mutating func mapping(map: Map) {
self.status <- map["status"]
self.response <- map["response"]
}
}
struct Utility : Mappable {
var code: String?
var packages: [Package]?
init?(map: Map) { }
mutating func mapping(map: Map) {
self.code <- map["code"]
self.packages <- map["packages"]
}
}
struct Package : Mappable {
var id: Int?
var name: String?
var code: String?
var price: Int?
init?(map: Map) { }
mutating func mapping(map: Map) {
self.id <- map["package_id"]
self.name <- map["package_name"]
self.code <- map["package_code"]
self.price <- map["package_price"]
}
}
Then you can use it to map JSON to your object like this:
// data is what your get in the dataTask's completion block
let jsonString = String(data: data, encoding: .utf8)!
if let jsonResponse = JSONResponse(JSONString: jsonString),
let utilities = jsonResponse.response {
print(utilities)
}
Everything has to be declared optional because you don't know if the value will be in the JSON string or not.
In Swift 4
Things get a lot simpler in Swift 4 with the new Encodable and Decodable protocols. Both combined to form the Encodable protocol (yes, protocol composition is a new thing in Swift 4). You no longer need ObjectMapper in Swift 4.
You still need to define your data model first:
struct JSONResponse : Codable {
var status: String
var response: [Utility]
}
struct Utility : Codable {
var code: String
var packages: [Package]
private enum CodingKeys: String, CodingKey {
case code = "utility_code"
case packages
}
}
struct Package : Codable {
var id: Int
var name: String
var code: String
var price: Int
private enum CodingKeys: String, CodingKey {
case id = "package_id"
case name = "package_name"
case code = "package_code"
case price = "package_price"
}
}
And here's how you use the new JSONDecoder struct in Swift 4:
let jsonRepsonse = try! JSONDecoder().decode(JSONResponse.self, from: data)
let utilities = jsonRepsonse.response
print(utilities)
So what's going on here?
Both ObjectMapper and Codable map the values in JSON to your data model.
In ObjectMapper, you have to explicitly list which property maps to which value in JSON in a function named mapping(map:):
mutating func mapping(map: Map) {
self.id <- map["package_id"]
self.name <- map["package_name"]
self.code <- map["package_code"]
self.price <- map["package_price"]
}
<- is the "mapping operator" defined by ObjectMapper (it's not in the Standard Library).
With Swift 4's Codable, the compiler automates a lot of things for you, which makes it appear magical and confusing at first. Essentially you define your mappings in an enum called CodingKeys:
struct JSONResponse : Codable {
var status: String
var response: [Utility]
// Define your JSON mappings here
private enum CodingKeys: String, CodingKey {
case status = "status"
case response = "response"
}
}
struct Package : Codable {
var id: Int
var name: String
var code: String
var price: Int
// Define your JSON mappings here
private enum CodingKeys: String, CodingKey {
case id = "package_id"
case name = "package_name"
case code = "package_code"
case price = "package_price"
}
}
If your JSON keys are the same as your property name, like in the JSONResponse struct, you don't have to define the explicit value for each case and you can simply write:
struct JSONResponse : Codable {
var status: String
var response: [Utility]
private enum CodingKeys: String, CodingKey {
case status // no explicit value here
case response
}
}
Better yet, since every JSON key is the same as your property name, you can omit the CodingKeys enum all together and let the compiler handle that for you:
// All you need to do is to conform it to Codable
// CodingKeys is generated automatically
struct JSONResponse : Codable {
var status: String
var response: [Utility]
}
To learn more about Codable, watch the What's new in Foundation session from WWDC 2017.