Deserialize a JSON array to a Swift array of objects - ios

Question

I am new to Swift, and am not able to figure out how to deserialize a JSON array to an array of Swift objects. I'm able to deserialize a single JSON user to a Swift user object fine, but just not sure how to do it with a JSON array of users.
Here is my User.swift class:
class User {
var id: Int
var firstName: String?
var lastName: String?
var email: String
var password: String?
init (){
id = 0
email = ""
}
init(user: NSDictionary) {
id = (user["id"] as? Int)!
email = (user["email"] as? String)!
if let firstName = user["first_name"] {
self.firstName = firstName as? String
}
if let lastName = user["last_name"] {
self.lastName = lastName as? String
}
if let password = user["password"] {
self.password = password as? String
}
}
}
Here's the class where I'm trying to deserialize the JSON:
//single user works.
Alamofire.request(.GET, muURL/user)
.responseJSON { response in
if let user = response.result.value {
var swiftUser = User(user: user as! NSDictionary)
}
}
//array of users -- not sure how to do it. Do I need to loop?
Alamofire.request(.GET, muURL/users)
.responseJSON { response in
if let users = response.result.value {
var swiftUsers = //how to get [swiftUsers]?
}
}

Answer 1

The best approach is the use Generic Response Object Serialization provided by Alamofire here is an example :
1) Add the extension in your API Manager or on a separate file
public protocol ResponseObjectSerializable {
init?(response: NSHTTPURLResponse, representation: AnyObject)
}
extension Request {
public func responseObject<T: ResponseObjectSerializable>(completionHandler: Response<T, NSError> -> Void) -> Self {
let responseSerializer = ResponseSerializer<T, NSError> { request, response, data, error in
guard error == nil else { return .Failure(error!) }
let JSONResponseSerializer = Request.JSONResponseSerializer(options: .AllowFragments)
let result = JSONResponseSerializer.serializeResponse(request, response, data, error)
switch result {
case .Success(let value):
if let
response = response,
responseObject = T(response: response, representation: value)
{
return .Success(responseObject)
} else {
let failureReason = "JSON could not be serialized into response object: \(value)"
let error = Error.errorWithCode(.JSONSerializationFailed, failureReason: failureReason)
return .Failure(error)
}
case .Failure(let error):
return .Failure(error)
}
}
return response(responseSerializer: responseSerializer, completionHandler: completionHandler)
}
}
public protocol ResponseCollectionSerializable {
static func collection(response response: NSHTTPURLResponse, representation: AnyObject) -> [Self]
}
extension Alamofire.Request {
public func responseCollection<T: ResponseCollectionSerializable>(completionHandler: Response<[T], NSError> -> Void) -> Self {
let responseSerializer = ResponseSerializer<[T], NSError> { request, response, data, error in
guard error == nil else { return .Failure(error!) }
let JSONSerializer = Request.JSONResponseSerializer(options: .AllowFragments)
let result = JSONSerializer.serializeResponse(request, response, data, error)
switch result {
case .Success(let value):
if let response = response {
return .Success(T.collection(response: response, representation: value))
} else {
let failureReason = "Response collection could not be serialized due to nil response"
let error = Error.errorWithCode(.JSONSerializationFailed, failureReason: failureReason)
return .Failure(error)
}
case .Failure(let error):
return .Failure(error)
}
}
return response(responseSerializer: responseSerializer, completionHandler: completionHandler)
}
}
2) update your model object like this:
final class User: ResponseObjectSerializable, ResponseCollectionSerializable {
let username: String
let name: String
init?(response: NSHTTPURLResponse, representation: AnyObject) {
self.username = response.URL!.lastPathComponent!
self.name = representation.valueForKeyPath("name") as! String
}
static func collection(response response: NSHTTPURLResponse, representation: AnyObject) -> [User] {
var users: [User] = []
if let representation = representation as? [[String: AnyObject]] {
for userRepresentation in representation {
if let user = User(response: response, representation: userRepresentation) {
users.append(user)
}
}
}
return users
}
}
3) then you can use it like that :
Alamofire.request(.GET, "http://example.com/users")
.responseCollection { (response: Response<[User], NSError>) in
debugPrint(response)
}
Source: Generic Response Object Serialization
Useful Link: Alamofire JSON Serialization of Objects and Collections

Answer 2

Since you are using Alamofire to make your requests why don't you give a chance to Hearst-DD ObjectMapper it has an Alamofire extension AlamofireObjectMapper. I think it'll save you time!

Answer 3

I would loop through them then add each user to an array (preferably a property of the VC and not an instance variable) but here is an example.
Alamofire.request(.GET, "YourURL/users")
.responseJSON { response in
if let users = response.result.value {
for user in users {
var swiftUser = User(user: user as! NSDictionary)
//should ideally be a property of the VC
var userArray : [User]
userArray.append(swiftUser)
}
}
}

Answer 4

You could also try EVReflection https://github.com/evermeer/EVReflection
It's even more simple, i.e. to parse JSON (code snippet taken from EVReflection link):
let json:String = "{
\"id\": 24,
\"name\": \"Bob Jefferson\",
\"friends\": [{
\"id\": 29,
\"name\":
\"Jen Jackson\"}]}"
you can use this class:
class User: EVObject {
var id: Int = 0
var name: String = ""
var friends: [User]? = []
}
in this way:
let user = User(json: json)