How can I use Swift’s Codable to encode into a dictionary?
If you don't mind a bit of shifting of data around you could use something like this:
extension Encodable {
func asDictionary() throws -> [String: Any] {
let data = try JSONEncoder().encode(self)
guard let dictionary = try JSONSerialization.jsonObject(with: data, options: .allowFragments) as? [String: Any] else {
throw NSError()
}
return dictionary
}
}
Or an optional variant
extension Encodable {
var dictionary: [String: Any]? {
guard let data = try? JSONEncoder().encode(self) else { return nil }
return (try? JSONSerialization.jsonObject(with: data, options: .allowFragments)).flatMap { $0 as? [String: Any] }
}
}
Assuming Foo
conforms to Codable
or really Encodable
then you can do this.
let struct = Foo(a: 1, b: 2)
let dict = try struct.asDictionary()
let optionalDict = struct.dictionary
If you want to go the other way(init(any)
), take a look at this Init an object conforming to Codable with a dictionary/array
Implement Codable for an Array of Dictionary with failable responses
This is a solution widely based on this intriguing answer of Rob Napier.
The goal of TitleKey
and the two Decoder
extensions is to map dictionaries with arbitrary keys to arrays adding the key as title
property.
struct TitleKey: CodingKey {
let stringValue: String
init?(stringValue: String) { self.stringValue = stringValue }
var intValue: Int? { return nil }
init?(intValue: Int) { return nil }
}
extension Decoder {
func currentTitle() throws -> String {
guard let titleKey = codingPath.last as? TitleKey else {
throw DecodingError.dataCorrupted(.init(codingPath: codingPath,
debugDescription: "Not in titled container"))
}
return titleKey.stringValue
}
}
extension Decoder {
func decodeTitledElements<Element: Decodable>(_ type: Element.Type) throws -> [Element] {
let titles = try container(keyedBy: TitleKey.self)
return titles.allKeys.compactMap { title in
return try? titles.decode(Element.self, forKey: title)
}
}
}
I modified the decodeTitledElements
function to decode only those dictionaries whose value represents the RecordSuper
struct filtering the other keys.
Here are the structs.
struct Root : Decodable {
let data : [Containers]
}
struct Containers: Decodable {
let containers: [RecordSuper]
init(from decoder: Decoder) throws {
self.containers = try decoder.decodeTitledElements(RecordSuper.self)
}
}
struct RecordSuper : Decodable {
let title : String
let dateTime : Date
let medication : String
let record : Record
enum CodingKeys: String, CodingKey {
case dateTime = "date_time", medication, record
}
init(from decoder: Decoder) throws {
self.title = try decoder.currentTitle()
let container = try decoder.container(keyedBy: CodingKeys.self)
self.dateTime = try container.decode(Date.self, forKey: .dateTime)
self.medication = try container.decode(String.self, forKey: .medication)
self.record = try container.decode(Record.self, forKey: .record)
}
}
struct Record : Decodable {
let status : String
}
Now decode the JSON assuming jsonData
is the JSON as Data
let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .millisecondsSince1970
let result = try decoder.decode(Root.self, from: jsonData
print(result.data)
How can I make a Decodable object from a dictionary?
You're on the right path.
import Foundation
public protocol Parsable: Decodable {
init(dict: [String: Any]) throws
}
struct LinkModel: Parsable {
var href: String
var text: String
init(dict: [String: Any]) throws {
href = "/store/options.aspx"
text = "Buy"
}
}
struct ResponseModel: Parsable {
var link: LinkModel?
let showCell: Bool
enum CodingKeys : String, CodingKey {
case link
case showCell = "show"
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
let linkResponses = try container.decode([LinkModel].self, forKey: .link)
link = linkResponses.first
showCell = try container.decode(Bool.self, forKey: .showCell)
}
init(dict: [String: Any]) throws {
let jsonData = try JSONSerialization.data(withJSONObject: dict, options: [])
// 1.
let decoder = JSONDecoder()
// 2.
let result = try decoder.decode(ResponseModel.self, from: jsonData)
// 3.
self = result
}
}
let jsonText = """
{
"show": true,
"link": [
{
"text": "Buy",
"href": "/store/options.aspx"
}
]
}
"""
// test standard Decodable instantiation
let jsonData = jsonText.data(using: .utf8)!
let model = try! JSONDecoder().decode(ResponseModel.self, from: jsonData)
print(model.link?.href)
All I did was:
- create a JSONdecoder object.
- use that JSONdecoder to decode an object of type
ResponseModel
- assign the result of the decoding to
self
. This way all properties ofself
are assigned.
Am I able to add a member-wise initializer to a Codable-conforming object?
Your code is correct, double check whether you actually have a public initializer not a private one.
I put this into my Xcode Playground and everything works as expected:
public class A: Codable {
var aString: String?
public init(input: String?) {
self.aString = input
}
}
let a = A(input: "123")
How to decode a property with type of JSON dictionary in Swift [45] decodable protocol
With some inspiration from this gist I found, I wrote some extensions for UnkeyedDecodingContainer
and KeyedDecodingContainer
. You can find a link to my gist here. By using this code you can now decode any Array<Any>
or Dictionary<String, Any>
with the familiar syntax:
let dictionary: [String: Any] = try container.decode([String: Any].self, forKey: key)
or
let array: [Any] = try container.decode([Any].self, forKey: key)
Edit: there is one caveat I have found which is decoding an array of dictionaries [[String: Any]]
The required syntax is as follows. You'll likely want to throw an error instead of force casting:
let items: [[String: Any]] = try container.decode(Array<Any>.self, forKey: .items) as! [[String: Any]]
EDIT 2: If you simply want to convert an entire file to a dictionary, you are better off sticking with api from JSONSerialization as I have not figured out a way to extend JSONDecoder itself to directly decode a dictionary.
guard let json = try JSONSerialization.jsonObject(with: data, options: []) as? [String: Any] else {
// appropriate error handling
return
}
The extensions
// Inspired by https://gist.github.com/mbuchetics/c9bc6c22033014aa0c550d3b4324411a
struct JSONCodingKeys: CodingKey {
var stringValue: String
init?(stringValue: String) {
self.stringValue = stringValue
}
var intValue: Int?
init?(intValue: Int) {
self.init(stringValue: "\(intValue)")
self.intValue = intValue
}
}
extension KeyedDecodingContainer {
func decode(_ type: Dictionary<String, Any>.Type, forKey key: K) throws -> Dictionary<String, Any> {
let container = try self.nestedContainer(keyedBy: JSONCodingKeys.self, forKey: key)
return try container.decode(type)
}
func decodeIfPresent(_ type: Dictionary<String, Any>.Type, forKey key: K) throws -> Dictionary<String, Any>? {
guard contains(key) else {
return nil
}
guard try decodeNil(forKey: key) == false else {
return nil
}
return try decode(type, forKey: key)
}
func decode(_ type: Array<Any>.Type, forKey key: K) throws -> Array<Any> {
var container = try self.nestedUnkeyedContainer(forKey: key)
return try container.decode(type)
}
func decodeIfPresent(_ type: Array<Any>.Type, forKey key: K) throws -> Array<Any>? {
guard contains(key) else {
return nil
}
guard try decodeNil(forKey: key) == false else {
return nil
}
return try decode(type, forKey: key)
}
func decode(_ type: Dictionary<String, Any>.Type) throws -> Dictionary<String, Any> {
var dictionary = Dictionary<String, Any>()
for key in allKeys {
if let boolValue = try? decode(Bool.self, forKey: key) {
dictionary[key.stringValue] = boolValue
} else if let stringValue = try? decode(String.self, forKey: key) {
dictionary[key.stringValue] = stringValue
} else if let intValue = try? decode(Int.self, forKey: key) {
dictionary[key.stringValue] = intValue
} else if let doubleValue = try? decode(Double.self, forKey: key) {
dictionary[key.stringValue] = doubleValue
} else if let nestedDictionary = try? decode(Dictionary<String, Any>.self, forKey: key) {
dictionary[key.stringValue] = nestedDictionary
} else if let nestedArray = try? decode(Array<Any>.self, forKey: key) {
dictionary[key.stringValue] = nestedArray
}
}
return dictionary
}
}
extension UnkeyedDecodingContainer {
mutating func decode(_ type: Array<Any>.Type) throws -> Array<Any> {
var array: [Any] = []
while isAtEnd == false {
// See if the current value in the JSON array is `null` first and prevent infite recursion with nested arrays.
if try decodeNil() {
continue
} else if let value = try? decode(Bool.self) {
array.append(value)
} else if let value = try? decode(Double.self) {
array.append(value)
} else if let value = try? decode(String.self) {
array.append(value)
} else if let nestedDictionary = try? decode(Dictionary<String, Any>.self) {
array.append(nestedDictionary)
} else if let nestedArray = try? decode(Array<Any>.self) {
array.append(nestedArray)
}
}
return array
}
mutating func decode(_ type: Dictionary<String, Any>.Type) throws -> Dictionary<String, Any> {
let nestedContainer = try self.nestedContainer(keyedBy: JSONCodingKeys.self)
return try nestedContainer.decode(type)
}
}
Codable [String: Any] dictionary
Is it possible to use Codable with [String: Any] dictionary?
no, you can't with Codable but you can make this dictionary in a new model.
Replace
public var message: [String: Any]?
with
public var message: MessageModel?
struct MessageModel: Codable { }
How to encode/decode a dictionary with Codable values for storage in UserDefaults?
You are mixing up NSCoding
and Codable
. The former requires a subclass of NSObject
, the latter can encode the structs and classes directly with JSONEncoder
or ProperListEncoder
without any Keyedarchiver
which also belongs to NSCoding
.
Your struct can be reduced to
struct Company: Codable {
var name : String
var initials : String
var logoURL : URL?
var brandColor : String?
}
That's all, the CodingKeys and the other methods are synthesized. I would at least declare name
and initials
as non-optional.
To read and save the data is pretty straightforward. The corresponding CompanyDefaults
struct is
struct CompanyDefaults {
static private let companiesKey = "companiesKey"
static var companies: [String:Company] = {
guard let data = UserDefaults.standard.data(forKey: companiesKey) else { return [:] }
return try? JSONDecoder.decode([String:Company].self, from: data) ?? [:]
}() {
didSet {
guard let data = try? JSONEncoder().encode(companies) else { return }
UserDefaults.standard.set(data, forKey: companiesKey)
}
}
}
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