I am trying to transform "Object Mapper" to "Codable". My response which comes from service includes NSArray which includes custom objects. I need to use NSArray and NSDictionary in Codable Class. But, i failed.I tried to use third party library like AnyCodable, but, i failed again. I can't change the response on server side. It must come as Array. I must use Array. Do you have any suggestion or information?
class Person : Codable { //Error 1
var name: String?
var data: NSArray?
private enum CodingKeys : String, CodingKey {
case name
case data
}
func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encode(name, forKey: .name)
try container.encode(data, forKey: .data) //Error 2
}
func decode(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
self.name = try container.decode(String.self, forKey: .name)
self.data = try container.decode(NSArray.self, forKey: .data) //Error 3
}
}
Error 1: "Type 'Person' does not conform to protocol 'Decodable'"
Error 2: "Argument type 'NSArray' does not conform to expected type 'Encodable'"
Error 3: "Instance method 'decode(_:forKey:)' requires that 'NSArray' conform to 'Decodable'"
Sample response is here.All items in the array don't have the same contents. Every item in array has different type.
{
"data": [
{
"languageCode": "EN",
"deviceInformation": {
"screenSize": "height:812.0 width:375.0",
"connectionType": "wifi",
"deviceType": "iPhone",
"deviceCode": "D01D304C-D05C-4443-9A92-031C55D14XC7",
"operatingSystemVersion": "12.2",
"applicationVersion": "1.0"
},
"lastUpdatedParamDate": "13.05.2019 14:44:24",
"skipOptionalUpdate": 0
}
]
}
When you make it
var data: NSArray?
it's a bridged objective - c type that have Any as the type of elements and Any doesn't conform to Codable so explicitly make it the type like
var data:[SomeModel]
or use JSONSerialization instead
struct Root: Codable {
let data: [Model]
}
struct Model: Codable {
let languageCode: String
let deviceInformation: DeviceInformation
let lastUpdatedParamDate: String
let skipOptionalUpdate: Int
}
struct DeviceInformation: Codable {
let screenSize, connectionType, deviceType, deviceCode: String
let operatingSystemVersion, applicationVersion: String
}
let eventData = try JSONDecoder().decode(Root.self, from: data)
if you have more attributes you can add them , if some returns nil in some cases make them optional , but if the type changes then no way with Codable
Related
In my custom initializer I'd like to decode a dictionary from JSON and then assign its values to properties in the class. To my surprise, compiler does not allow me to decode the dictionary, I get the error:
Value of protocol type 'Any' cannot conform to 'Decodable'; only struct/enum/class types can conform to protocols
If I try to decode dictionary of type [String: Decodable] the error message says:
Value of protocol type 'Decodable' cannot conform to 'Decodable'; only struct/enum/class types can conform to protocols
My initializer looks like this:
public let total: Int
required init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
...
if let dict = try container.decodeIfPresent([String: Any].self, forKey: .tracks),
let value = dict["total"] as? Int { // Error is displayed at this line
total = value
} else {
total = 0
}
...
}
When I looked for the answer I found this answer and according to it the code above should not cause any problems.
What you are looking for is nestedContainer. It helps you "skip" a hierarchy level in your JSON. Ie: let's imagine that in your code, it's all in the same level (one struct), but in the JSON, it's not, there is a sub dictionary.
For test purpose, your JSON might look like:
{
"title": "normal",
"tracks": {
"name": "myName",
"total": 3
}
}
If we want in our model:
struct TestStruct: Codable {
let title: String
let name: String
let total: Int
}
We need to use nestedContainer(keyedBy: forKey:):
extension TestStruct {
enum TopLevelKeys: String, CodingKey {
case title
case tracks
}
enum NestedLevelCodingKeys: String, CodingKey {
case name
case total
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: TopLevelKeys.self)
self.title = try container.decode(String.self, forKey: .title)
let subcontainer = try container.nestedContainer(keyedBy: NestedLevelCodingKeys.self, forKey: TopLevelKeys.tracks)
self.name = try subcontainer.decode(String.self, forKey: .name)
self.total = try subcontainer.decode(Int.self, forKey: .total) //You can use here a `decodeIfPresent()` if needed, use default values, etc.
}
}
In your sample, you used decodeIfPresent() for the subdictionary. It's unclear if it was for test purpose, or if the sub dictionary was sometimes not present.
If that's the case and you can have a JSON like this:
{
"title": "normal"
}
Then, before calling nestedContainer(keyedBy: forKey:), use if container.contains(TopLevelKeys.tracks) {} and set default values if needed in the else case.
I'm trying to parse a json that looks like this using decodable:
{
"count": 1,
"results": [
{
"title": 1,
"content": "Bla"
} ]
}
My problem is that I don't want to make a class that has a count property just to be able to use the decoder. I want to parse only the results part I don't care about the count.
So my question is, can decodable.decode somehow only parse a part of the result json. I mean a certain key path instead of the whole json ? And I want to do it using Decodable.
In a nutshell I don't want this:
class IncidentWrapper: Codable{
var count: Int
var incident: [Incident]
}
What I would Imagine is to have this:
decodable.decode([Incident].self, from: response.data, forKey: "results")
Thanks
let me see what I can suggest:
struct Result: Codeable {
var id: Int
var message: String
var color: String
var type: String
enum CodingKeys: String, CodingKey {
case results
}
enum NestedResultKeys: String, CodingKey {
case id, message, color, type
}
}
extension Result: Decodable {
init(from decoder: Decoder) throws {
let result = try decoder.container(keyedBy: CodingKeys.self)
let nestedResult = try result.nestedContainer(keyedBy: NestedResultKeys.self, forKey: .result)
id = try nestedResult.decode(Int.self, forKey: .id)
message = try nestedResult.decode(String.self, forKey: .message)
color = try nestedResult.decode(String.self, forKey: .color)
type = try nestedResult.decode(String.self, forKey: .id)
}
}
See this documentation for more insight
https://developer.apple.com/documentation/swift/swift_standard_library/encoding_decoding_and_serialization
Hope it helps your project!
You probably is looking for JSONSerialization class. This is an example how it works:
if let json = try? JSONSerialization.jsonObject(with: data, options: []) as? [String : Any] {
if let results = json["results"] as? [Incident] {
print(results.count)
}
}
You can define a generic wrapper for once and use everywhere.
It will work as a generic wrapper for results key only.
protocol ResultsDecodable: Decodable{
associatedtype T: Decodable
var results: [T] {get}
}
struct Result<Element: Decodable>: ResultsDecodable{
typealias T = Element
var results: [Element]
}
Extend JSONDecoder to get results output.
extension JSONDecoder {
func resultDecode<T>(_ type: Result<T>.Type, from data: Data) throws -> [T] where T : Decodable{
let model = try! decode(type, from: data)
return model.results
}
}
And use like this
var str = #"{"count": 1,"results": [{"title": 1,"content": "Bla"}, {"title": 2,"content": "Bla"} ]}"#
class Incident: Decodable{
let title: Int
let content: String
}
let indicents = (try! JSONDecoder().resultDecode(Result<Incident>.self, from: str.data(using: .utf8)!))
See how it makes everything more complex. BETTER USE IncidentWrapper!!!
You only need to use the keys you care about. Just leave off the count. Don't make it part of your struct.
You will only get errors if you can't find a key in the json that you are expecting in the struct. You can avoid this too, though, if you make it an optional in the struct.
I have the following object
struct Properties: Decodable {
var id: String?
var value: String?
var color: String?
}
In the first request to server I get the following response
{
"id":"1",
"color":"red"
}
And after another request I get
{
"id":"1", // the id of the object props is meant for
"props":{
"value":"my value" // I can get any property here
}
}
After the two requests I should have the object with all properties set
By now I decode the second request as following
struct SetAttr: Decodable {
let id: String
let props: [String : Any]
enum SetAttrCodingKeys: String, CodingKey {
case id
case props
}
init(from decoder: Decoder) throws {
let container = try! decoder.container(keyedBy: SetAttrCodingKeys.self)
props = try! container.decode([String : Any].self, forKey: .props)
id = try! container.decode(String.self, forKey: .id)
}
}
But I do not know how to parse props dictionary and set the properties on the first object. I am willing to use a decoding library, but I did not find any that can do this
EDIT:
This is how I tried to set the properties from dictionary, but the solution is not scalable
var myObject: Properties
properties = setAttr.props // [String:Any]
let keys = properties.keys
keys.forEach { key in
if let value = properties[key] {
switch key {
case "value":
myObject.value = value as? String
case "color":
myObject.color = value as? String
default:
break
}
}
}
Just use JSONSerialization which parses whatever you throw at it into arrays and dictionaries. That frees you from all the problems you have with strangely formatted JSON.
For example, the second request will be parsed as a dictionary with two keys "id" and "props", and "props" has a value which is again a dictionary with one key "value" and a value "my value".
And please stop using try! That will cause your app to crash instantly if any input is not expected. Unexpected inputs should be handled, not lead to a crash.
There are various way to do this, but one possible way could be something like this:
struct SecAttr: Decodable {
let id: String
var props: Properties?
private enum CodingKeys: String, CodingKey {
case id
case props
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
id = try container.decode(String.self, forKey: .id)
if let props = try container.decodeIfPresent(Properties.self, forKey: .props) {
self.props = props
} else {
// decode Properties from the same object
self.props = try Properties(from: decoder)
}
}
}
struct Properties: Decodable {
var value: String?
var color: String?
mutable update(from props: Properties) {
value = props.value ?? value
color = color.value ?? color
}
}
Now you can decode your original object and after getting updated properties, just update them on the original.
I have the following json string:
{"weight":[{"bmi":24.75,"date":"2020-01-20","logId":1000,"source":"API","time":"23:59:59","weight":200}]}
I want to convert it to a Swift object in order to access the different values. Here is what I am trying to do, I have these structs setup:
struct FitbitResponseModel: Decodable {
let weight: [FitbitResponseData]
}
struct FitbitResponseData: Decodable {
let bmi: Int
let date: String
let logId: Int
let source: String
let time: String
let weight: Int
}
And then I have this method to decode the json string:
func parseJSON(data: Data) -> FitbitResponseModel? {
var returnValue: FitbitResponseModel?
do {
returnValue = try JSONDecoder().decode(FitbitResponseModel.self, from: data)
} catch {
print("Error took place: \(error.localizedDescription).")
}
return returnValue
}
However when I try to run it I get the error that the data couldn’t be read because it isn’t in the correct format. What am I doing wrong? Any help is appreciated.
Thanks in advance!
change
let bmi: Int
to
let bmi: Double
beacuse it's value is coming out to be 24.75 in your response if any variable type doesn't match to JSON response whole model wouldn't map in Codable protocol (Encodable and Decodable)
Talk to your API developer. 000 is not a valid representation of a number for json. It needs to be either 0 or 0.0. You can lint your json at https://jsonlint.com . If you really need to work around this I suggest doing a string replacement on 000, with 0, before you parse the data.
Json is n't valid because logId value in your json is n't valid.
{
"weight": [{
"bmi": 24.75,
"date": "2020-01-20",
"logId": 100,
"source": "API",
"time": "23:59:59",
"weight": 200
}]
}
One really neat feature of this auto-generated conformance is that if you define an enum in your type called "CodingKeys" (or use a type alias with this name) that conforms to the CodingKey protocol – Swift will automatically use this as the key type. This therefore allows you to easily customise the keys that your properties are encoded/decoded with.
struct Base: Codable {
let weight : [Weight]?
enum CodingKeys: String, CodingKey {
case weight = "weight"
}
init(from decoder: Decoder) throws {
let values = try decoder.container(keyedBy: CodingKeys.self)
weight = try values.decodeIfPresent([Weight].self, forKey: .weight)
}
}
struct Weight : Codable {
let bmi : Double?
let date : String?
let logId : Int?
let source : String?
let time : String?
let weight : Int?
enum CodingKeys: String, CodingKey {
case bmi = "bmi"
case date = "date"
case logId = "logId"
case source = "source"
case time = "time"
case weight = "weight"
}
init(from decoder: Decoder) throws {
let values = try decoder.container(keyedBy: CodingKeys.self)
bmi = try values.decodeIfPresent(Double.self, forKey: .bmi)
date = try values.decodeIfPresent(String.self, forKey: .date)
logId = try values.decodeIfPresent(Int.self, forKey: .logId)
source = try values.decodeIfPresent(String.self, forKey: .source)
time = try values.decodeIfPresent(String.self, forKey: .time)
weight = try values.decodeIfPresent(Int.self, forKey: .weight)
}
}
Hope that will help!
or you can use SwiftyJSON lib: https://github.com/SwiftyJSON/SwiftyJSON
I am trying to parse an array of heterogeneous objects using Codable. These objects are also unkeyed as well. I should note that I have the container structure correct, because it DOES loop through and print "it is type1" at all correct times as seen below. I just can't figure out how to access the actual object. Here is my code:
var data: [Any]
public init(from decoder: Decoder) throws {
var container = try! decoder.container(keyedBy: CodingKeys.self).nestedUnkeyedContainer(forKey: .data)
while !container.isAtEnd {
var itemContainer = try container.nestedContainer(keyedBy: CodingKeys.self)
let itemType = try itemContainer.decode(String.self, forKey: .type)
switch itemType {
case "type1":
print("it is type1")
// this does not compile, but is what I need
//let objectOfItem1 = try itemContainer.decode(Type1.self)
// this compiles, but doesn't work because there is no key with these objects
//let objectOfItem1 = try itemContainer.decode(Type1, forKey: .type)
default:
print("test:: it is the default")
}
}
}
private enum CodingKeys: String, CodingKey {
case data
case type
}
And here is the JSON I am trying to decode (many properties committed for clarity):
"contents" : {
"data" : [
{
"type" : "type1",
"id" : "6a406cdd7a9cace5"
},
{
"type" : "type2",
"id" : "ljhdgsouilghoipsu"
}
]
}
How can I correctly get my individual Type1 objects out of this structure?
I think the easy way to get around the heterogenous data is to use an enum as an interim type to wrap your various Item types (which all need to Codable):
To allow myself to test this I've changed your json slightly to give me more heterogenous data for testing. I've used:
let json = """
{
"contents": {
"data": [
{
"type": "type1",
"id": "6a406cdd7a9cace5"
},
{
"type": "type2",
"dbl": 1.01
},
{
"type": "type3",
"int": 5
}
]
}
}
and then created the three final types represented by this json
struct Item1: Codable {
let type: String
let id: String
}
struct Item2: Codable {
let type: String
let dbl: Double
}
struct Item3: Codable {
let type: String
let int: Int
}
To allow decoding the multiple types in a type-safe way (as required by Codable) you need to use a single type that can represent (or wrap) the possible options. An enum with associated values works nicely for this
enum Interim {
case type1 (Item1)
case type2 (Item2)
case type3 (Item3)
case unknown //to handle unexpected json structures
}
So far, so good, but then it gets slightly more complicated when it comes to creating the Interim from the JSON. It will need a CodingKey enum which represents all the possible keys for all the Item# types, and then it will need to decode the JSON linking all these keys to their respective types and data:
extension Interim: Decodable {
private enum InterimKeys: String, CodingKey {
case type
case id
case dbl
case int
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: InterimKeys.self)
let type = try container.decode(String.self, forKey: .type)
switch type {
case "type1":
let id = try container.decode(String.self, forKey: .id)
let item = Item1(type: type, id: id)
self = .type1(item)
case "type2":
let dbl = try container.decode(Double.self, forKey: .dbl)
let item = Item2(type: type, dbl: dbl)
self = .type2(item)
case "type3":
let int = try container.decode(Int.self, forKey: .int)
let item = Item3(type: type, int: int)
self = .type3(item)
default: self = .unknown
}
}
}
This provides the mechanism for decoding the heterogenous components, now we just need to deal with the higher-level keys. As we have a Decodable Interim type this is straightforward:
struct DataArray: Decodable {
var data: [Interim]
}
struct Contents: Decodable {
var contents: DataArray
}
This now means the json can be decoded like this...
let data = Data(json.utf8)
let decoder = JSONDecoder()
do {
let contents = try decoder.decode(Contents.self, from: data)
print(contents)
} catch {
print("Failed to decode JSON")
print(error.localizedDescription)
}
This successfully decodes the data into a nested structure where the major component is the array of Interim types with their associated Item# objects. The above produces the following output, showing these nested types:
Contents(contents: testbed.DataArray(data: [testbed.Interim.type1(testbed.Item1(type: "type1", id: "6a406cdd7a9cace5")), testbed.Interim.type2(testbed.Item2(type: "type2", dbl: 1.01)), testbed.Interim.type3(testbed.Item3(type: "type3", int: 5))]))
I think there should be an even safer way to do this with Type Erasure to provide a more extensible solution, but I've not got my head around that fully yet.
I think you need use this structure:
struct A: Codable {
let contents: B?
enum CodingKeys: String, CodingKey {
case contents
}
struct B: Codable {
let data: [C]?
enum CodingKeys: String, CodingKey {
case data
}
struct C: Codable {
let type : String?
let id : String?
}
}
}
extension A {
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
let contents = try container.decodeIfPresent(B.self, forKey: .contents)
self.init(contents: contents)
}
}
I'd like to add to flanker's answer an improvement for cleaner approach to avoid having all possible keys to be stored under Interim's CodingKey. Here is an updated Interim
enum Interim: Decodable {
case item1(Item1)
case item2(Item2)
case item3(Item3)
case unknown
init(from decoder: Decoder) throws {
let typeContainer = try decoder.container(keyedBy: Key.self)
// Fallback for any unsupported types
guard let type = try? typeContainer.decode(ItemType.self, forKey: .type) else {
self = .unknown
return
}
// Let corresponding Decodable Item to be initialized from the same decoder.
switch type {
case .type1: self = .item1(try .init(from: decoder))
case .type2: self = .item2(try .init(from: decoder))
case .type3: self = .item3(try .init(from: decoder))
}
}
/// These are values for Item.type
private enum ItemType: String, Decodable {
case type1
case type2
case type3
}
private enum Key: CodingKey {
case type
}
}