I am having a problem with initializing Struct with JSON Data received from the URLRequest in Swift 3.
The protocol JSONDecodable:
protocol JSONDecodable {
init?(JSON: [String : AnyObject])
}
The struct is as follows and it implements extension that conforms to JSONDecodable:
struct Actor {
let ActorID: String
let ActorName: String
}
extension Actor: JSONDecodable {
init?(JSON: [String : AnyObject]) {
guard let ActorID = JSON["ActorID"] as? String, let ActorName = JSON["ActorName"] as? String else {
return nil
}
self.ActorID = ActorID
self.ActorName = ActorName
}
}
Then I have the following code where I try to map an array of dictionaries to struct Actor. I think that I mix Swift 2 and Swift 3 syntax together.
guard let actorsJSON = json?["response"] as? [[String : AnyObject]] else {
return
}
return actorsJSON.flatMap { actorDict in
return Actor(JSON: actorDict)
}
However, I get the following error: 'flatMap' produces '[SegmentOfResult.Iterator.Element]', not the expected contextual result type 'Void' (aka '()')
Any help would be greatly appreciated!
As #dfri mentioned, you haven't showed us your function signature but I'm also guessing you haven't specified the return type of the function.
This is how I would do it though
typealias JSONDictionary = [String: AnyObject]
extension Actor {
func all(_ json: JSONDictionary) -> [Actor]? {
guard let actorsJSON = json["response"] as? [JSONDictionary] else { return nil }
return actorsJSON.flatMap(Actor.init).filter({ $0 != nil }).map({ $0! })
}
}
Related
I have classes like these:
class MyDate
{
var year : String = ""
var month : String = ""
var day : String = ""
init(year : String , month : String , day : String) {
self.year = year
self.month = month
self.day = day
}
}
class Lad
{
var firstName : String = ""
var lastName : String = ""
var dateOfBirth : MyDate?
init(firstname : String , lastname : String , dateofbirth : MyDate) {
self.firstName = firstname
self.lastName = lastname
self.dateOfBirth = dateofbirth
}
}
class MainCon {
func sendData() {
let myDate = MyDate(year: "1901", month: "4", day: "30")
let obj = Lad(firstname: "Markoff", lastname: "Chaney", dateofbirth: myDate)
let api = ApiService()
api.postDataToTheServer(led: obj)
}
}
class ApiService {
func postDataToTheServer(led : Lad) {
// here i need to json
}
}
And I would like to turn a Lad object into a JSON string like this:
{
"firstName":"Markoff",
"lastName":"Chaney",
"dateOfBirth":
{
"year":"1901",
"month":"4",
"day":"30"
}
}
EDIT - 10/31/2017: This answer mostly applies to Swift 3 and possibly earlier versions. As of late 2017, we now have Swift 4 and you should be using the Encodable and Decodable protocols to convert data between representations including JSON and file encodings. (You can add the Codable protocol to use both encoding and decoding)
The usual solution for working with JSON in Swift is to use dictionaries. So you could do:
extension Date {
var dataDictionary {
return [
"year": self.year,
"month": self.month,
"day": self.day
];
}
}
extension Lad {
var dataDictionary {
return [
"firstName": self.firstName,
"lastName": self.lastName,
"dateOfBirth": self.dateOfBirth.dataDictionary
];
}
}
and then serialize the dictionary-formatted data using JSONSerialization.
//someLad is a Lad object
do {
// encoding dictionary data to JSON
let jsonData = try JSONSerialization.data(withJSONObject: someLad.dataDictionary,
options: .prettyPrinted)
// decoding JSON to Swift object
let decoded = try JSONSerialization.jsonObject(with: jsonData, options: [])
// after decoding, "decoded" is of type `Any?`, so it can't be used
// we must check for nil and cast it to the right type
if let dataFromJSON = decoded as? [String: Any] {
// use dataFromJSON
}
} catch {
// handle conversion errors
}
If you just need to do this for few classes, providing methods to turn them into dictionaries is the most readable option and won't make your app noticeably larger.
However, if you need to turn a lot of different classes into JSON it would be tedious to write out how to turn each class into a dictionary. So it would be useful to use some sort of reflection API in order to be able to list out the properties of an object. The most stable option seems to be EVReflection. Using EVReflection, for each class we want to turn into json we can do:
extension SomeClass: EVReflectable { }
let someObject: SomeClass = SomeClass();
let someObjectDictionary = someObject.toDictionary();
and then, just like before, we can serialize the dictionary we just obtained to JSON using JSONSerialization. We'll just need to use object.toDictionary() instead of object.dataDictionary.
If you don't want to use EVReflection, you can implement reflection (the ability to see which fields an object has and iterate over them) yourself by using the Mirror class. There's an explanation of how to use Mirror for this purpose here.
So, having defined either a .dataDictionary computed variable or using EVReflection's .toDictionary() method, we can do
class ApiService {
func postDataToTheServer(lad: Lad) {
//if using a custom method
let dict = lad.dataDictionary
//if using EVReflection
let dict = lad.toDictionary()
//now, we turn it into JSON
do {
let jsonData = try JSONSerialization.data(withJSONObject: dict,
options: .prettyPrinted)
// send jsonData to server
} catch {
// handle errors
}
}
}
May this GitHub code will help you.
protocol SwiftJsonMappable {
func getDictionary() -> [String: Any]
func JSONString() -> String
}
extension SwiftJsonMappable {
//Convert the Swift dictionary to JSON String
func JSONString() -> String {
do {
let jsonData = try JSONSerialization.data(withJSONObject: self.getDictionary(), options: .prettyPrinted)
// here "jsonData" is the dictionary encoded in JSON data
let jsonString = String(data: jsonData, encoding: .utf8) ?? ""
// here "decoded" is of type `Any`, decoded from JSON data
return jsonString
// you can now cast it with the right type
} catch {
print(error.localizedDescription)
}
return ""
}
//Convert Swift object to Swift Dictionary
func getDictionary() -> [String: Any] {
var request : [String : Any] = [:]
let mirror = Mirror(reflecting: self)
for child in mirror.children {
if let lable = child.label {
//For Nil value found for any swift propery, that property should be skipped. if you wanna print nil on json, disable the below condition
if !checkAnyContainsNil(object: child.value) {
//Check whether is custom swift class
if isCustomType(object: child.value) {
//Checking whether its an array of custom objects
if isArrayType(object: child.value) {
if let objects = child.value as? [AMSwiftBase] {
var decodeObjects : [[String:Any]] = []
for object in objects {
//If its a custom object, nested conversion of swift object to Swift Dictionary
decodeObjects.append(object.getDictionary())
}
request[lable] = decodeObjects
}
}else {
//Not an arry, and custom swift object, convert it to swift Dictionary
request[lable] = (child.value as! AMSwiftBase).getDictionary()
}
}else {
request[lable] = child.value
}
}
}
}
return request
}
//Checking the swift object is swift base type or custom Swift object
private func isCustomType(object : Any) -> Bool {
let typeString = String(describing: type(of: object))
if typeString.contains("String") || typeString.contains("Double") || typeString.contains("Bool") {
return false
}
return true
}
//checking array
private func isArrayType(object : Any) -> Bool {
let typeString = String(describing: type(of: object))
if typeString.contains("Array"){
return true
}
return false
}
//Checking nil object
private func checkAnyContainsNil(object : Any) -> Bool {
let value = "\(object)"
if value == "nil" {
return true
}
return false
}
}
https://github.com/anumothuR/SwifttoJson
What I'm trying to do is retrieve json data(which is in array format) and check to see if my local array already contains the data, if it does move on to the next value in the JSON data until their is a value that the array doesn't contain then append it to the array. This data in the array must be in order. I'm attempting to do this now but get the error:
Type 'ResultsGenrePosters' does not conform to protocol 'Sequence'
This is what it looks like:
public struct ResultsGenrePosters: Decodable {
public let results : [GenrePosters]?
public init?(json: JSON) {
results = "results" <~~ json
}
}
public struct GenrePosters: Decodable {
public let poster : String
public init? (json: JSON) {
guard let poster: String = "poster_path" <~~ json
else {return nil}
self.poster = poster
}
static func updateGenrePoster(genreID: NSNumber, urlExtension: String, completionHandler:#escaping (_ details: [String]) -> Void){
var posterArray: [String] = []
let nm = NetworkManager.sharedManager
nm.getJSONData(type:"genre/\(genreID)", urlExtension: urlExtension, completion: {
data in
if let jsonDictionary = nm.parseJSONData(data)
{
guard let genrePosters = ResultsGenrePosters(json: jsonDictionary)
else {
print("Error initializing object")
return
}
guard let posterString = genrePosters.results?[0].poster
else {
print("No such item")
return
}
for posterString in genrePosters {
if posterArray.contains(posterString){continue
} else { posterArray.append(posterString) } //This is where the error happens
}
}
completionHandler(posterArray)
})
}
}
Alt + click on genrePosters and what does it tell you? It should say its ResultsGenrePosters because thats what the error is saying. Now look at the type of posterArray; its an array of String, not Array ResultsGenrePosters. I think you mean to write for poster in genrePosters and have confused yourself about the types because you wrote for posterString in genrePosters.
Maybe you want to use map to transform genrePosters into a [String] ?
This transforms your posterArray, if it exists into an array containing just the poster names. If it doesn't exist you get an empty array. This only works if poster is String. If its String? you should use flatMap instead.
let posterNames = genrePosters.results?.map { $0.poster } ?? [String]()
I'm getting this error which I can't figure out how to fix:
Contextual type 'AnyObject' cannot be used with dictionary literal
I've searched on the internet but failed to find an answer. Here's my code:
struct Sweet {
let key:String!
let content:String!
let addedByUser:String!
let itemReft:FIRDatabaseReference?
init (content:String, addedByUser:String, key:String = "") {
self.key = key
self.content = content
self.addedByUser = addedByUser
self.itemReft = nil
}
init (snapshot:FIRDataSnapshot) {
key = snapshot.key
itemReft = snapshot.ref
if let dict = snapshot.value as? NSDictionary, let postContent = dict["content"] as? String {
content = postContent
} else {
content = ""
}
if let dict = snapshot.value as? NSDictionary, let postUser = dict["addedByUser"] as? String {
addedByUser = postUser
} else {
addedByUser = ""
}
}
func toAnyObject() -> AnyObject {
return ["content":content, "addedByUser":addedByUser]
}
The error happens at this line:
return ["content":content, "addedByUser":addedByUser]
I've been following this tutorial iOS Swift Tutorial: Get started with Firebase and an App like Twitter
Thanks for your time!
You have to cast the literal to the desired type
func toAnyObject() -> Any {
return ["content":content, "addedByUser":addedByUser] as Any
}
But - no offense – casting up a specific type to something more unspecific is silly. Why not
func toDictionary() -> [String:String] {
return ["content":content, "addedByUser":addedByUser]
}
I have response JSON of multitype objects from API.
It has type property inside. Now I'm trying to apply some kind of automated mapping basing on type property, but I can't make it work in any means.
private let modelClassMap = [
"first_type": First.self
]
func createModelWithDictionary(json: [String: AnyObject]) -> [AnyObject] {
var items: [AnyObject]
if let items = json["items"] as? [[String: AnyObject]] {
for item in items {
if let typeString = item["type"] as? String {
var Type = self.modelClassMap[typeString]
items.append(Mapper<Type>().map(item))
}
}
}
return items
}
error I am getting is that Type is not a type
What you're trying to do is not really possible, because template's associated types are not runtime. Compiler needs to know a type at compile time.
We can do it a bit differently, using enums:
enum ModelClassMap: String {
case FirstType = "first_type"
func map(item: [String: AnyObject]) -> AnyObject? {
switch self {
case FirstType:
return Mapper<First>().map(item)
}
}
}
And in your for-loop you can try convert string to enum:
func createModelWithDictionary(json: [String: AnyObject]) -> [AnyObject] {
var mappedItems: [AnyObject] = []
if let items = json["items"] as? [[String: AnyObject]] {
items.forEach() {
if let typeString = $0["type"] as? String,
let mappedType = ModelClassMap(rawValue: typeString),
let mappedObject = mappedType.map($0) {
// mappedObject represents an instance of required object, represented by "type"
mappedItems.append(mappedObject)
}
}
}
return mappedItems
}
I have a struct like
struct Channel {
var id : Int = 0
var name = ""
}
and I am getting json from URL as
{"channel_list":[{"channel_id":0,"channel_name":"test1"},{"channel_id":0,"channel_name":"test2"}]}
However I am not able to get data as
func parseJson(anyObj:AnyObject) -> Array<Channel>{
var list:Array<Channel> = []
if anyObj is Array<AnyObject> {
var b:Channel = Channel()
for json in anyObj as! Array<AnyObject>{
b.id = (json["channel_id"] as AnyObject? as? Int) ?? 0
b.name = (json["channel_name"] as AnyObject? as? String) ?? ""
list.append(b)
}
}
return list
}
//read code
let anyObj: AnyObject? = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions(0),error: nil) as AnyObject?
println(anyObj)
if let myobj=anyObj["channel_list"] as AnyObject {
self.Channellist=self.parseJson(anyObj!)
}
Whats wrong with this?
First, instead of using AnyObject, you should cast the JSON response as a Dictionary: [NSObject:AnyObject] then safe cast the result of anyObj["channel_list"] to an Array of Dictionaries [[NSObject:AnyObject]], because this is your JSON response format.
Then you need to use this type in your parseJSON function. We're also simplifying it while we're at it, because there's no need to do weird castings anymore.
Also, you were passing the wrong argument to your function (you used anyObj instead of myObj).
struct Channel {
var id : Int = 0
var name = ""
}
func parseJson(anyObj: [[NSObject:AnyObject]]) -> Array<Channel>{
var list: Array<Channel> = []
var b: Channel = Channel()
for json in anyObj {
b.id = (json["channel_id"] as? Int) ?? 0
b.name = (json["channel_name"] as? String) ?? ""
list.append(b)
}
return list
}
if let anyObj = NSJSONSerialization.JSONObjectWithData(data!, options: NSJSONReadingOptions(0),error: nil) as? [NSObject:AnyObject] {
if let myobj = anyObj["channel_list"] as? [[NSObject:AnyObject]] {
self.Channellist=self.parseJson(myobj)
}
}
There's still room for improvement: you could create an initializer for your Struct, for example, and also create a typealias for the response types, use map to create the list, etc.
Here's how I would do it with Swift 2:
struct Channel {
var id : Int
var name: String
init?(JSON: [NSObject: AnyObject]?) {
guard let channelID = json["channel_id"] as? Int, let channelName = json["channel_name"] as? String
else { name = ""; id = 0; return nil }
name = channelName
id = channelID
}
}
func parseJSON(array: [[NSObject:AnyObject]]) -> [Channel?] {
return array.map { Channel(JSON: $0) }
// If you don't want to return optionals to channel you can do this instead:
// return array.map { Channel(JSON: $0) }.filter { $0 != nil }.map { $0! }
}
// And in the caller
do {
guard let dict = try NSJSONSerialization.JSONObjectWithData(data!, options: []) as? [NSObject : AnyObject]
else { throw NSError(domain ... // Setup error saying JSON wasn't parsed. }
guard let arrayContents = dict["channel_list"] as? [[NSObject:AnyObject]]
else { throw NSError(domain ... // Setup error saying array wasn't found. }
let channels = parseJSON(arrayContents)
}
catch {
print(error)
}