I'm fairly new to this. Anyway, here we go:
I have JSON data that comes from an API. For the sake of this question, I have simplified it greatly. You can run the following code in a Playground.
import UIKit
struct Book: Codable {
let image: String
}
// this comes from my API
let jsonString = "{ \"image\" = \"someURL\" }"
print(jsonString) // { "image" = "someURL" }
// convert String to Data
let jsonData = jsonString.data(using: .utf8)
// decode data (in my project, I catch the error, of course)
let decoder = JSONDecoder()
let decodingResult = try? decoder.decode(Book.self, from: jsonData!)
print(decodingResult) // nil
As you can see, I'm trying to decode my JSON-String into an Object (my Struct), but the Decoder always returns nil.
Can someone point me in the right direction?
Thank you.
Your current jsonString isn't a proper JSON. Change it to "{ \"image\": \"someURL\" }", and it should work. For more information on JSON syntax, check this manual.
Related
This question already has answers here:
Decoding Error -- Expected to decode Dictionary<String, Any> but found an array instead
(2 answers)
Closed 1 year ago.
I'm working on a creative project, and I'm trying to decode content from an API database using Swift's JSONDecoder() function. I've built my structs, a getData() function, and I've set up a do-try-catch for the JSONDecoder() function. I'm having difficulty understanding what I'm doing to get the error I'm getting.
Here are my structs:
struct Response: Codable {
let foundRecipes: [Recipe]
let foundIngredients: [Ingredient]
}
struct Recipe: Codable {
let id: Int
let title: String
let image: String
let imageType: String
let usedIngredientCount: Int
let missedIngredientCount: Int
let missedIngredients: [Ingredient]
let usedIngredients: [Ingredient]
let unusedIngredients: [Ingredient]
let likes: Int
}
struct Ingredient: Codable {
let id: Int
let amount: Int
let unit: String
let unitLong: String
let unitShort: String
let aisle: String
let name: String
let original: String
let originalString: String
let origianalName: String
let metaInformation: [String]
let meta: [String]
let image: String
}
Here's my getData() function:
func getData(from url: String) {
URLSession.shared.dataTask(with: URL(string: url)!, completionHandler: { data, response, error in
guard let data = data, error == nil else {
print("something went wrong.")
return
}
var result: Response?
do {
result = try JSONDecoder().decode(Response.self, from: data)
}
catch {
print("")
print(String(describing: error)) // Right here is where the error hits.
}
guard let json = result else {
return
}
print(json.foundRecipes)
}).resume()
}
Here's a link to the API's documentation. The URL I'm calling in getData() links to the same structure of search as shown in their example: https://spoonacular.com/food-api/docs#Search-Recipes-by-Ingredients — and here's a screenshot of the url results for the exact search I'm working on: https://imgur.com/a/K3Rn9SZ
And finally, here's the full error that I'm catching:
typeMismatch(Swift.Dictionary<Swift.String, Any>, Swift.DecodingError.Context(codingPath: [], debugDescription: "Expected to decode Dictionary<String, Any> but found an array instead.", underlyingError: nil))
My understanding of this error is that it's saying I told the JSONDecoder() to look for a Dictionary of <String, Any>, but it's at the link and only seeing an array. I'm confused, because I don't know where it thinks I'm providing a dictionary. Where am I screwing up? Not looking for specific code changes, just some guidance on what I'm missing.
Thanks in advance :)
As you can see in your image of the API data and in the API documentation you linked to, the API is returning an array (in the documentation, for example, you can see that it is surrounded by [...]). In fact, it looks like the API returns an array of Recipe.
So, you can change your decoding call to this:
var result: [Recipe]?
do {
result = try JSONDecoder().decode([Recipe].self, from: data)
print(result)
} catch {
print(error)
}
Perhaps your idea for Response came from somewhere else, but the keys foundRecipes or foundIngredients don't show up in this particular API call.
Also, thanks to #workingdog's for a useful comment about changing amount to a Double instead of an Int in your model.
I'm having a problem figuring out how to handle dynamic keys with a single value one level deep. I've seen a few examples but they appear to handle other cases.
Here's an example.
[
{ "asdofjiodi": "asdofidj.com" },
{ "sadjlkj": "iejjol.com" },
{ "ijijwjljlijl": "adsijf.com" },
{ "jgncmkz": "mlkjaoijf.com" }
]
Any ideas on how I accomplish this with Codable or CodingKey? This is what I'd like for the end result.
["asdofidj.com", "iejjol.com", "adsijf.com", "mlkjaoijf.com"]
let url = Bundle.main.url(forResource: "file", withExtension: "json")!
let data = try! Data(contentsOf: url)
let decoder = JSONDecoder()
// NOTE: The below line doesn't work because I'm not sure how to do the encoding/decoding
try? decoder.decode([[String: String]].self, from: data)
First of all, is not a valid JSON. A "Valid JSON" can be a JSON Array (multiple json objects) or a single JSON object (starts and ends with { and })
After cleaning this...
You are trying to make a dictionary (json object) from a data. You don't need JSONDecoder to accomplish this. Try using JSONSerialization with jsonObject static function...
let data = Data("{\"asdofjiodi\": \"asdofidj.com\",\"sadjlkj\": \"iejjol.com\",\"ijijwjljlijl\": \"adsijf.com\",\"jgncmkz\": \"mlkjaoijf.com\"}".utf8)
let json = try? JSONSerialization.jsonObject(with: data) as? [String: Any]
let values = json?.map({ $1 })
print(values)
I Hope I helped!
JSONSerialization Apple documentation
Here is a minimal working example, given the JSON in your question:
let json = """
[
{ "asdofjiodi": "asdofidj.com" },
{ "sadjlkj": "iejjol.com" },
{ "ijijwjljlijl": "adsijf.com" },
{ "jgncmkz": "mlkjaoijf.com" }
]
"""
let data = Data(json.utf8)
let decoder = JSONDecoder()
do {
let decodedJson = try decoder.decode([[String: String]].self, from: data)
let values = decodedJson.compactMap(\.values.first)
print(values)
} catch {
print("Error: \(error.localizedDescription)")
}
If this doesn't appear to work for you, it may be related to how you load in the JSON.
What I want to do:
I want to get an array from UserDefaults that I saved beforehand and append a custom object to it. Afterwards I want to encode it as a Data-type again and set this as the UserDefaults Key again.
My problem:
The encoding part is what is not working as intended for me.
It says: -[__SwiftValue encodeWithCoder:]: unrecognized selector sent to instance 0x60000011a540
But I do not know how to fix this.
Below is my code for more context:
do {
let decoded = defaults.object(forKey: "ExArray") as! Data
var exo = try NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(decoded) as! [Exerc]
exo.append(datas[indexPath.row])
let enco = try NSKeyedArchiver.archivedData(withRootObject: exo, requiringSecureCoding: false) <- Here is the error
defaults.set(enco, forKey: "ExArray")
} catch {
print("Error encoding custom object NOSEARCHO")
}
This is how Exerc looks:
struct Exerc: Codable {
var title: String
var exID: String
}
Seems like you are not using the archiver features, so why don't you just use the codable?
do {
let key = "ExArray"
let decoded = defaults.data(forKey: key)!
var exo = try JSONDecoder().decode([Exerc].self, from: decoded)
exo.append(datas[indexPath.row])
let enco = try JSONEncoder().encode(exo)
defaults.set(enco, forKey: key)
} catch {
print("Error encoding/decoding custom object NOSEARCHO", error)
}
It just a simple refactored MVP of the original code, but you can even work a bit on this and make it human readable right in the plist file!
I am attempting to decode my JSON response data from type: AnyObject? back into something that can be printed out in the console / interacted with.
reading back the data, before decoding prints projectName.GameData
Here is the breakdown, data comes back from the response as type: Any? Because it sent up as
class GameData : Codable {
var isPlayerOneTurn: Bool!
var wasCreated: Bool!
var playerOne: String!
var playerTwo: String!
var board: [[Int]]!
init() {
}
}
The current error I am getting when attempting to decode is Cannot convert value of type 'GameData' to expected argument type 'Data'
code :
let decoder = JSONDecoder()
let dataTest = try? decoder.decode(GameData.self, from: data)
Am I missing a correct init() method on the GameData class?
UPDATE:
data was changed to type Data here: thank you #rmaddy for the comment pointing this out.
let data = data as? Data
let decoder = JSONDecoder()
let dataTest = try? decoder.decode(GameData.self, from: data!)
print("data: \(String(describing: dataTest))")
the print line still shows data: Optional(projectName.GameData)
What is wrong here still, not allowing me to view the values of the class GameData?
The print line mentioned in the question, was the value of the game object decode.. That was all XCode would print out - the name of the original object before decoding. Using dataTest.myValue worked when accessing data from the object.
API gives me back a variable that has type Any. It looks like this when I print it.
{
"sender" : "Kira",
"created" : "08.05.2018",
"text" : "Cncncm"
}
I tried to use SwiftyJSON to cast it like this let mydata = JSON(data) but it failes. I tried to use Swift 4 decoding technique but that failed as well. I tried to do this let myData = data as? Dictionary<String, String> but it fails again.
I am clueless what to do here. Any tips or solutions?
Finally a chance to demonstrate one of the Codable protocols hidden gems. Please run the following in a Playground:
import Cocoa
let jsonData = """
{
"sender" : "Kira",
"created" : "08.05.2018",
"text" : "Cncncm"
}
""".data(using: .utf8)!
struct SenderText: Codable {
let sender: String
let created: Date
let text: String
}
let dayFormatter = DateFormatter()
dayFormatter.dateFormat = "dd.MM.yyyy"
let date = dayFormatter.date(from:"08.05.2018")
let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .formatted(dayFormatter)
do {
let sendText = try decoder.decode(SenderText.self, from: jsonData)
print(sendText)
} catch {
print(error)
}
The sheer elegance of how easy it is to define such an intricate parser mapping a messy JSON-string to your favourite struct will hardly ever stop to amaze me. No matter how weird your date format looks, it is hardly more than 3 lines away from being parsed during the process.
There is something in regard to casting you should note though: In Swift, as in most object oriented languages, you can only cast something to something else if (and only if) it already is something else in the first place (but that knowledge has been lost somewhere). Since your String is "just" a String (in disguise of an Any maybe) you won't be able to cast it to anything else. However the Codable protocol provides you with a terrific means to decode from the Strings Data with astonishing ease. This process should not be mistaken as a cast, even if it looks largely the same. It is the creation and initialisation of another, more fittingly structured object from a simple piece of Data that you are likely to have gotten from your average web service of choice.
Great so far, at least in my book.
You can parse it like this as it's a json string
let trd = yourVar as? String
if let data = trd?.data(using: String.Encoding.utf8) {
do {
var content = try JSONSerialization.jsonObject(with: data, options: .allowFragments) as! [String:String]
print(content)
}
catch let error as NSError {
print(error)
}
}