I'm attempting to parse the following json schema of array of items, itemID may not be empty. How do I make an item nil id itemID does not exist in the JSON?
[{
"itemID": "123",
"itemTitle": "Hello"
},
{},
...
]
My decodable classes are as follows:
public struct Item: : NSObject, Codable {
let itemID: String
let itemTitle: String?
}
private enum CodingKeys: String, CodingKey {
case itemID
case itemTitle
}
required init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
itemID = try container.decode(String.self, forKey: .itemID)
itemTitle = try container.decodeIfPresent(String.self, forKey: .itemTitle)
super.init()
}
}
First of all, itemID is an Int and not String in your JSON response. So the struct Item looks like,
public struct Item: Codable {
let itemID: Int?
let itemTitle: String?
}
Parse the JSON like,
if let data = data {
do {
let items = try JSONDecoder().decode([Item].self, from: data).filter({$0.itemID == nil})
print(items)
} catch {
print(error)
}
}
In the above code you can simply filter out the items with itemID == nil.
Related
This is a simplified model that is decoded from JSON:
struct Info: Decodable {
var text: String
var num: Int
}
struct Root: Decodable {
let info: Info
}
Sometimes I need to decode Info.text or Info.num only but sometimes both of them and to support all options I've made similar structs for decoding e.g:
// For text only
struct InfoText: Decodable {
var text: String
}
struct RootText: Decodable {
let info: InfoText
}
// For num only
struct InfoNum: Decodable {
var num: Int
}
struct RootNum: Decodable {
let info: InfoNum
}
This approach produces much cloned code and runtime checks to process the structs so is it possible to decode provided coding keys only with the single struct?
It's possible to provide any contextual information to the decoder with userInfo property and in this case we can pass an array of coding keys and use this info in the decoding process:
struct Info: Decodable {
var text: String?
var num: Int?
static var keys = CodingUserInfoKey(rawValue: "keys")!
enum CodingKeys: String, CodingKey {
case text, num
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
guard let keys = decoder.userInfo[Self.keys] as? [CodingKeys] else {
return
}
if keys.contains(.text) {
text = try container.decode(String.self, forKey: .text)
}
if keys.contains(.num) {
num = try container.decode(Int.self, forKey: .num)
}
}
}
struct Root: Decodable {
let info: Info
}
let json = #"{ "info" : { "text": "Hello", "num": 20 } }"#.data(using: .utf8)!
let decoder = JSONDecoder()
let keys: [Info.CodingKeys] = [.text]
decoder.userInfo[Info.keys] = keys
let root = try decoder.decode(Root.self, from: json)
print(root)
// Outputs:
Root(info: Info(text: Optional("Hello"), num: nil))
I have the below json and I want to create model for the json with codable.
{
id = 1;
name = "abc";
empDetails = {
data = [{
address = "xyz";
ratings = 2;
"empId" = 6;
"empName" = "def";
}];
};
}
Model
struct Root: Codable {
let id: Int
let name: String
let empDetails:[Emp]
struct Emp: Codable {
let address: String
let ratings: Int
let empId: Int
let empName: String
}
}
I don't need the key data. I want to set the value of data to empDetails property
How can I do this with init(from decoder: Decoder) throws method?
Simply create enum CodingKeys and implement init(from:) in struct Root to get that working.
struct Root: Decodable {
let id: Int
let name: String
let empDetails: [Emp]
enum CodingKeys: String, CodingKey {
case id, name, empDetails, data
}
struct Emp: Codable {
let address: String
let ratings: Int
let empId: Int
let empName: String
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
id = try container.decode(Int.self, forKey: .id)
name = try container.decode(String.self, forKey: .name)
let details = try container.nestedContainer(keyedBy: CodingKeys.self, forKey: .empDetails)
empDetails = try details.decode([Emp].self, forKey: .data)
}
}
I have an API that will sometimes return a specific key value (in this case id) in the JSON as an Int and other times it will return that same key value as a String. How do I use codable to parse that JSON?
struct GeneralProduct: Codable {
var price: Double!
var id: String?
var name: String!
private enum CodingKeys: String, CodingKey {
case price = "p"
case id = "i"
case name = "n"
}
init(price: Double? = nil, id: String? = nil, name: String? = nil) {
self.price = price
self.id = id
self.name = name
}
}
I keep getting this error message: Expected to decode String but found a number instead. The reason that it returns a number is because the id field is empty and when the id field is empty it defaults to returning 0 as an ID which codable identifies as a number. I can basically ignore the ID key but codable does not give me the option to ignore it to my knowledge. What would be the best way to handle this?
Here is the JSON. It is super simple
Working
{
"p":2.12,
"i":"3k3mkfnk3",
"n":"Blue Shirt"
}
Error - because there is no id in the system, it returns 0 as a default which codable obviously sees as a number opposed to string.
{
"p":2.19,
"i":0,
"n":"Black Shirt"
}
struct GeneralProduct: Codable {
var price: Double?
var id: String?
var name: String?
private enum CodingKeys: String, CodingKey {
case price = "p", id = "i", name = "n"
}
init(price: Double? = nil, id: String? = nil, name: String? = nil) {
self.price = price
self.id = id
self.name = name
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
price = try container.decode(Double.self, forKey: .price)
name = try container.decode(String.self, forKey: .name)
do {
id = try String(container.decode(Int.self, forKey: .id))
} catch DecodingError.typeMismatch {
id = try container.decode(String.self, forKey: .id)
}
}
}
let json1 = """
{
"p":2.12,
"i":"3k3mkfnk3",
"n":"Blue Shirt"
}
"""
let json2 = """
{
"p":2.12,
"i":0,
"n":"Blue Shirt"
}
"""
do {
let product = try JSONDecoder().decode(GeneralProduct.self, from: Data(json2.utf8))
print(product.price ?? "nil")
print(product.id ?? "nil")
print(product.name ?? "nil")
} catch {
print(error)
}
edit/update:
You can also simply assign nil to your id when your api returns 0:
do {
let value = try container.decode(Int.self, forKey: .id)
id = value == 0 ? nil : String(value)
} catch DecodingError.typeMismatch {
id = try container.decode(String.self, forKey: .id)
}
This is a possible solution with MetadataType, the nice thing is that can be a general solution not for GeneralProduct only, but for all the struct having the same ambiguity:
struct GeneralProduct: Codable {
var price:Double?
var id:MetadataType?
var name:String?
private enum CodingKeys: String, CodingKey {
case price = "p"
case id = "i"
case name = "n"
}
init(price:Double? = nil, id: MetadataType? = nil, name: String? = nil) {
self.price = price
self.id = id
self.name = name
}
}
enum MetadataType: Codable {
case int(Int)
case string(String)
init(from decoder: Decoder) throws {
let container = try decoder.singleValueContainer()
do {
self = try .int(container.decode(Int.self))
} catch DecodingError.typeMismatch {
do {
self = try .string(container.decode(String.self))
} catch DecodingError.typeMismatch {
throw DecodingError.typeMismatch(MetadataType.self, DecodingError.Context(codingPath: decoder.codingPath, debugDescription: "Encoded payload not of an expected type"))
}
}
}
func encode(to encoder: Encoder) throws {
var container = encoder.singleValueContainer()
switch self {
case .int(let int):
try container.encode(int)
case .string(let string):
try container.encode(string)
}
}
}
this is the test:
let decoder = JSONDecoder()
var json = "{\"p\":2.19,\"i\":0,\"n\":\"Black Shirt\"}"
var product = try! decoder.decode(GeneralProduct.self, from: json.data(using: .utf8)!)
if let id = product.id {
print(id) // 0
}
json = "{\"p\":2.19,\"i\":\"hello world\",\"n\":\"Black Shirt\"}"
product = try! decoder.decode(GeneralProduct.self, from: json.data(using: .utf8)!)
if let id = product.id {
print(id) // hello world
}
Seamlessly decoding from either Int or String into the same property requires writing some code.
However, thanks to a (somewhat) new addition to the language,(property wrappers), you can make it quite easy to reuse this logic wherever you need it:
// note this is only `Decodable`
struct GeneralProduct: Decodable {
var price: Double
#Flexible var id: Int // note this is an Int
var name: String
}
The property wrapper and its supporting code can be implemented like this:
#propertyWrapper struct Flexible<T: FlexibleDecodable>: Decodable {
var wrappedValue: T
init(from decoder: Decoder) throws {
wrappedValue = try T(container: decoder.singleValueContainer())
}
}
protocol FlexibleDecodable {
init(container: SingleValueDecodingContainer) throws
}
extension Int: FlexibleDecodable {
init(container: SingleValueDecodingContainer) throws {
if let int = try? container.decode(Int.self) {
self = int
} else if let string = try? container.decode(String.self), let int = Int(string) {
self = int
} else {
throw DecodingError.dataCorrupted(.init(codingPath: container.codingPath, debugDescription: "Invalid int value"))
}
}
}
Original answer
You can use a wrapper over a string that knows how to decode from any of the basic JSON data types: string, number, boolean:
struct RelaxedString: Codable {
let value: String
init(_ value: String) {
self.value = value
}
init(from decoder: Decoder) throws {
let container = try decoder.singleValueContainer()
// attempt to decode from all JSON primitives
if let str = try? container.decode(String.self) {
value = str
} else if let int = try? container.decode(Int.self) {
value = int.description
} else if let double = try? container.decode(Double.self) {
value = double.description
} else if let bool = try? container.decode(Bool.self) {
value = bool.description
} else {
throw DecodingError.typeMismatch(String.self, .init(codingPath: decoder.codingPath, debugDescription: ""))
}
}
func encode(to encoder: Encoder) throws {
var container = encoder.singleValueContainer()
try container.encode(value)
}
}
You can then use this new type in your struct. One minor disadvantage would be that consumer of the struct will need to make another indirection to access the wrapped string. However that can be avoided by declaring the decoded RelaxedString property as private, and use a computed one for the public interface:
struct GeneralProduct: Codable {
var price: Double!
var _id: RelaxedString?
var name: String!
var id: String? {
get { _id?.value }
set { _id = newValue.map(RelaxedString.init) }
}
private enum CodingKeys: String, CodingKey {
case price = "p"
case _id = "i"
case name = "n"
}
init(price: Double? = nil, id: String? = nil, name: String? = nil) {
self.price = price
self._id = id.map(RelaxedString.init)
self.name = name
}
}
Advantages of the above approach:
no need to write custom init(from decoder: Decoder) code, which can become tedious if the number of properties to be decoded increase
reusability - RelaxedString can be seamlessly used in other structs
the fact that the id can be decoded from a string or an int remains an implementation detail, consumers of GeneralProduct don't know/care that the id can come from a string or an int
the public interface exposes string values, which keeps the consumer code simple as it will not have to deal with multiple types of data
I created this Gist which has a ValueWrapper struct that can handle
the following types
case stringValue(String)
case intValue(Int)
case doubleValue(Double)
case boolValue(Bool)
https://gist.github.com/amrangry/89097b86514b3477cae79dd28bba3f23
Based on #Cristik 's answer, I come with another solution using #propertyWrapper.
#propertyWrapper
struct StringForcible: Codable {
var wrappedValue: String?
enum CodingKeys: CodingKey {}
init(from decoder: Decoder) throws {
let container = try decoder.singleValueContainer()
if let string = try? container.decode(String.self) {
wrappedValue = string
} else if let integer = try? container.decode(Int.self) {
wrappedValue = "\(integer)"
} else if let double = try? container.decode(Double.self) {
wrappedValue = "\(double)"
} else if container.decodeNil() {
wrappedValue = nil
}
else {
throw DecodingError.typeMismatch(String.self, .init(codingPath: container.codingPath, debugDescription: "Could not decode incoming value to String. It is not a type of String, Int or Double."))
}
}
func encode(to encoder: Encoder) throws {
var container = encoder.singleValueContainer()
try container.encode(wrappedValue)
}
init() {
self.wrappedValue = nil
}
}
And usage is
struct SomeDTO: Codable {
#StringForcible var id: String?
}
Also works like -I think-
struct AnotherDTO: Codable {
var some: SomeDTO?
}
This question already has answers here:
Using codable with value that is sometimes an Int and other times a String
(5 answers)
Closed 6 months ago.
I have to decode a JSON with a big structure and a lot of nested arrays.
I have reproduced the structure in my UserModel file, and it works, except with one property (postcode) that is in a nested array (Location) that sometimes is an Int and some other is a String. I don't know how to handle this situation and tried a lot of different solutions.
The last one I've tried is from this blog https://agostini.tech/2017/11/12/swift-4-codable-in-real-life-part-2/
And it suggests using generics. But now I can't initialize the Location object without providing a Decoder():
Any help or any different approach would be appreciated.
The API call is this one: https://api.randomuser.me/?results=100&seed=xmoba
This is my UserModel File:
import Foundation
import UIKit
import ObjectMapper
struct PostModel: Equatable, Decodable{
static func ==(lhs: PostModel, rhs: PostModel) -> Bool {
if lhs.userId != rhs.userId {
return false
}
if lhs.id != rhs.id {
return false
}
if lhs.title != rhs.title {
return false
}
if lhs.body != rhs.body {
return false
}
return true
}
var userId : Int
var id : Int
var title : String
var body : String
enum key : CodingKey {
case userId
case id
case title
case body
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: key.self)
let userId = try container.decode(Int.self, forKey: .userId)
let id = try container.decode(Int.self, forKey: .id)
let title = try container.decode(String.self, forKey: .title)
let body = try container.decode(String.self, forKey: .body)
self.init(userId: userId, id: id, title: title, body: body)
}
init(userId : Int, id : Int, title : String, body : String) {
self.userId = userId
self.id = id
self.title = title
self.body = body
}
init?(map: Map){
self.id = 0
self.title = ""
self.body = ""
self.userId = 0
}
}
extension PostModel: Mappable {
mutating func mapping(map: Map) {
id <- map["id"]
title <- map["title"]
body <- map["body"]
userId <- map["userId"]
}
}
Well it's a common IntOrString problem. You could just make your property type an enum that can handle either String or Int.
enum IntOrString: Codable {
case int(Int)
case string(String)
init(from decoder: Decoder) throws {
let container = try decoder.singleValueContainer()
do {
self = try .int(container.decode(Int.self))
} catch DecodingError.typeMismatch {
do {
self = try .string(container.decode(String.self))
} catch DecodingError.typeMismatch {
throw DecodingError.typeMismatch(IntOrString.self, DecodingError.Context(codingPath: decoder.codingPath, debugDescription: "Encoded payload conflicts with expected type, (Int or String)"))
}
}
}
func encode(to encoder: Encoder) throws {
var container = encoder.singleValueContainer()
switch self {
case .int(let int):
try container.encode(int)
case .string(let string):
try container.encode(string)
}
}
}
As I have found mismatch of your model that you posted in your question and the one in the API endpoint you pointed to, I've created my own model and own JSON that needs to be decoded.
struct PostModel: Decodable {
let userId: Int
let id: Int
let title: String
let body: String
let postCode: IntOrString
// you don't need to implement init(from decoder: Decoder) throws
// because all the properties are already Decodable
}
Decoding when postCode is Int:
let jsonData = """
{
"userId": 123,
"id": 1,
"title": "Title",
"body": "Body",
"postCode": 9999
}
""".data(using: .utf8)!
do {
let postModel = try JSONDecoder().decode(PostModel.self, from: jsonData)
if case .int(let int) = postModel.postCode {
print(int) // prints 9999
} else if case .string(let string) = postModel.postCode {
print(string)
}
} catch {
print(error)
}
Decoding when postCode is String:
let jsonData = """
{
"userId": 123,
"id": 1,
"title": "Title",
"body": "Body",
"postCode": "9999"
}
""".data(using: .utf8)!
do {
let postModel = try JSONDecoder().decode(PostModel.self, from: jsonData)
if case .int(let int) = postModel.postCode {
print(int)
} else if case .string(let string) = postModel.postCode {
print(string) // prints "9999"
}
} catch {
print(error)
}
You can use generic like this:
enum Either<L, R> {
case left(L)
case right(R)
}
extension Either: Decodable where L: Decodable, R: Decodable {
init(from decoder: Decoder) throws {
let container = try decoder.singleValueContainer()
if let left = try? container.decode(L.self) {
self = .left(left)
} else if let right = try? container.decode(R.self) {
self = .right(right)
} else {
throw DecodingError.typeMismatch(Either<L, R>.self, .init(codingPath: decoder.codingPath, debugDescription: "Expected either `\(L.self)` or `\(R.self)`"))
}
}
}
extension Either: Encodable where L: Encodable, R: Encodable {
func encode(to encoder: Encoder) throws {
var container = encoder.singleValueContainer()
switch self {
case let .left(left):
try container.encode(left)
case let .right(right):
try container.encode(right)
}
}
}
And then declare postcode: Either<Int, String> and if your model is Decodable and all other fields are Decodable too no extra code would be needed.
If postcode can be both String and Int, you have (at least) two possible solutions for this issue. Firstly, you can simply store all postcodes as String, since all Ints can be converted to String. This seems like the best solution, since it seems highly unlikely that you'd need to perform any numeric operations on a postcode, especially if some postcodes can be String. The other solution would be creating two properties for postcode, one of type String? and one of type Int? and always only populating one of the two depending on the input data, as explained in Using codable with key that is sometimes an Int and other times a String.
The solution storing all postcodes as String:
struct PostModel: Equatable, Decodable {
static func ==(lhs: PostModel, rhs: PostModel) -> Bool {
return lhs.userId == rhs.userId && lhs.id == rhs.id && lhs.title == rhs.title && lhs.body == rhs.body
}
var userId: Int
var id: Int
var title: String
var body: String
var postcode: String
enum CodingKeys: String, CodingKey {
case userId, id, title, body, postcode
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
self.userId = try container.decode(Int.self, forKey: .userId)
self.id = try container.decode(Int.self, forKey: .id)
self.title = try container.decode(String.self, forKey: .title)
self.body = try container.decode(String.self, forKey: .body)
if let postcode = try? container.decode(String.self, forKey: .postcode) {
self.postcode = postcode
} else {
let numericPostcode = try container.decode(Int.self, forKey: .postcode)
self.postcode = "\(numericPostcode)"
}
}
}
try this extension
extension KeyedDecodingContainer{
public func decodeIfPresent(_ type: String.Type, forKey key: KeyedDecodingContainer<K>.Key) throws -> String?{
if let resStr = try? decode(type, forKey: key){
return resStr
}else{
if let resInt = try? decode(Int.self, forKey: key){
return String(resInt)
}
return nil
}
}
public func decodeIfPresent(_ type: Int.Type, forKey key: KeyedDecodingContainer<K>.Key) throws -> Int?{
if let resInt = try? decode(type, forKey: key){
return resInt
}else{
if let resStr = try? decode(String.self, forKey: key){
return Int(resStr)
}
return nil
}
}
}
example
struct Foo:Codable{
let strValue:String?
let intValue:Int?
}
let data = """
{
"strValue": 1,
"intValue": "1"
}
""".data(using: .utf8)
print(try? JSONDecoder().decode(Foo.self, from: data!))
it will print "Foo(strValue: Optional("1"), intValue: Optional(1))"
Lets say I have a dictionary like this:
{"user_data":{"id":3,"name":"Damian D","email":"aaa#aaa.pl"},"status":true}
How can I use Codable protocol to decode just user_data into such struct:
struct User: Codable {
private enum CodingKeys: String, CodingKey {
case id
case username = "name"
case email
}
let id: Int
let username: String
let email: String
}
Do I need to convert this sub dictionary into Data, or is there a easier way?
If you create nested Coding Keys you will accomplish decoding the response using only one data model.
Given the following JSON response:
let data = """
{
"user_data": {
"id":3,
"name":"Damian D",
"email":"aaa#aaa.pl"
},
"status":true
}
""".data(using: .utf8, allowLossyConversion: false)!
and the following data model:
public struct User: Decodable {
var id: Int
var name: String
var email: String
// MARK: - Codable
private enum RootCodingKeys: String, CodingKey {
case userData = "user_data"
enum NestedCodingKeys: String, CodingKey {
case id
case name
case email
}
}
required public init(from decoder: Decoder) throws {
let rootContainer = try decoder.container(keyedBy: RootCodingKeys.self)
let userDataContainer = try rootContainer.nestedContainer(keyedBy: RootCodingKeys.NestedCodingKeys.self, forKey: .userData)
self.id = try userDataContainer.decode(Int.self, forKey: .id)
self.name = try userDataContainer.decode(String.self, forKey: .name)
self.email = try userDataContainer.decode(String.self, forKey: .email)
}
}
You can decode your response into a single object:
let decoder = JSONDecoder()
let user = try? decoder.decode(User.self, from: data)
Create a new struct that has a userData member of type User.
struct Response: Codable {
private enum CodingKeys: String, CodingKey {
case userData = "user_data"
case status
}
let userData: User
let status: Bool
}