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![Inthe beginning...
if let id = json["id"] as? Int {
if let name = json["name"] as? String {
if let email = json["email"] as? String {
// create user
}
}
}](https://image.slidesharecdn.com/json-160202174229/75/Protocol-Oriented-JSON-Parsing-in-Swift-5-2048.jpg)
![Swift 1.2
if let id = json["id"] as? Int,
name = json["name"] as? String,
email = json["email"] as? String {
// create user
}
else {
// return some error, ex: `Result<T>`
}](https://image.slidesharecdn.com/json-160202174229/75/Protocol-Oriented-JSON-Parsing-in-Swift-6-2048.jpg)
![Swift 2
guard let id = json["id"] as? Int,
name = json["name"] as? String,
email = json["email"] as? String {
// throw some error
}
// create user](https://image.slidesharecdn.com/json-160202174229/75/Protocol-Oriented-JSON-Parsing-in-Swift-7-2048.jpg)
![Argo
extension User: Decodable {
static func decode(j: JSON) -> Decoded<User> {
return curry(User.init) // used to have to make a separate `make` function
<^> j <| "id"
<*> j <| "name"
<*> j <|? "email" // Use ? for parsing optional values
<*> j <| "role" // Custom types that also conform to Decodable just work
<*> j <| ["company", "name"] // Parse nested objects
<*> j <|| "friends" // parse arrays of objects
}
}
(https://github.com/thoughtbot/Argo)](https://image.slidesharecdn.com/json-160202174229/75/Protocol-Oriented-JSON-Parsing-in-Swift-8-2048.jpg)
![JSONArrays...
var pets = [Pet]()
if let petsObjects = json["pets"] as? [JSONObject] {
for petObject in petsObjects {
guard let id = petObject["id"] as? Int,
name = petObject["name"] as? String else {
continue // or throw error if less tolerant
}
let pet = Pet(id: id, name: name)
pets.append(pet)
}
}](https://image.slidesharecdn.com/json-160202174229/75/Protocol-Oriented-JSON-Parsing-in-Swift-13-2048.jpg)
![Wouldn'titbe greatif...
struct User : JSONObjectConvertible {
let id: Int
let name: String
let email: String?
let pets: [Pet]
init(json: JSONObject) throws {
id = try json.valueForKey("id")
name = try json.valueForKey("name")
email = try json.valueForKey("email")
pets = try json.valueForKey("pets")
}
}](https://image.slidesharecdn.com/json-160202174229/75/Protocol-Oriented-JSON-Parsing-in-Swift-15-2048.jpg)
Uploaded byJason Larsen
Protocol Oriented JSON Parsing in Swift
This document discusses the history and evolution of JSON parsing in Swift, from early approaches using optional binding to more recent solutions like Argo and JSONCodable that allow objects to be initialized directly from JSON. It covers techniques like using guard to handle errors, protocols like JSONObjectConvertible that simplify parsing, and challenges in parsing to Core Data models. Overall it presents different strategies for JSON parsing in Swift and evaluating tradeoffs between simplicity, robustness, and compatibility with tools like Core Data.
Protocol Oriented JSON Parsing in Swift
- 1. JSON Parsing by JaSONLarsen @jarsen
- 2. JSON Parsing by JaSONLarsen @jarsen
- 3. JSONValue Extraction by JaSONLarsen @jarsen
- 4.
- 5. Inthe beginning... if letid = json["id"] as? Int { if let name = json["name"] as? String { if let email = json["email"] as? String { // create user } } }
- 6. Swift 1.2 if letid = json["id"] as? Int, name = json["name"] as? String, email = json["email"] as? String { // create user } else { // return some error, ex: `Result<T>` }
- 7. Swift 2 guard letid = json["id"] as? Int, name = json["name"] as? String, email = json["email"] as? String { // throw some error } // create user
- 8. Argo extension User: Decodable{ static func decode(j: JSON) -> Decoded<User> { return curry(User.init) // used to have to make a separate `make` function <^> j <| "id" <*> j <| "name" <*> j <|? "email" // Use ? for parsing optional values <*> j <| "role" // Custom types that also conform to Decodable just work <*> j <| ["company", "name"] // Parse nested objects <*> j <|| "friends" // parse arrays of objects } } (https://github.com/thoughtbot/Argo)
- 10.
- 12.
- 13. JSONArrays... var pets =[Pet]() if let petsObjects = json["pets"] as? [JSONObject] { for petObject in petsObjects { guard let id = petObject["id"] as? Int, name = petObject["name"] as? String else { continue // or throw error if less tolerant } let pet = Pet(id: id, name: name) pets.append(pet) } }
- 14.
- 15. Wouldn'titbe greatif... struct User: JSONObjectConvertible { let id: Int let name: String let email: String? let pets: [Pet] init(json: JSONObject) throws { id = try json.valueForKey("id") name = try json.valueForKey("name") email = try json.valueForKey("email") pets = try json.valueForKey("pets") } }
- 16.
- 17.
- 18. Caveat: Core DataModels ForNSManagedObject subclasses JSONObjectConvertible won't really work because init is not so simple... public protocol JSONDecoding { func update(json: JSONObject) throws }
- 19. Caveat: Core DataModels classUser: NSManagedObject, JSONDecoding { @NSManaged var name: String @NSManaged var email: String func update(json: JSONObject) throws { try name = json.valueForKey("name") try email = json.valueForKey("email") } }
- 20. MatthewCheok'sJSONCodable extension User: JSONEncodable{ func toJSON() throws -> AnyObject { return try JSONEncoder.create({ (encoder) -> Void in try encoder.encode(id, key: "id") try encoder.encode(name, key: "full_name") try encoder.encode(email, key: "email") try encoder.encode(company, key: "company") try encoder.encode(friends, key: "friends") }) } } (https://github.com/matthewcheok/JSONCodable)
- 21. SpecialThanks » Bart Whiteley »Brian Mullen » BJ Homer » Derrick Hathaway » Dave DeLong » Mark Schultz » Tim Shadel
- 22. Resources » My blogjasonlarsen.me (look for No-Magic JSON series) » JaSON https://github.com/jarsen/JaSON » JaSON (extension on Dictionary) https:// github.com/bwhiteley/JaSON