SwiftUI decoding JSON from API

Question

I know there are already some articles regarding this issue, but I could not find anything related to my JSON.

This is how my JSON likes like:

{
  "message": {
    "affenpinscher": [],
    "african": [],
    "airedale": [],
    "akita": [],
    "appenzeller": [],
    "australian": [
      "shepherd"
    ],
    "basenji": []
  },
  "status: "succes"
}

So, if I understand it correctly it is dictionary because it starts with {, but what are the things inside the "message"?

This is my Dog.swift class where I am re-writing the JSON, but I am not sure if it is correct:

class Dog: Decodable, Identifiable {
    
    var message: Message?
    var status: String?
}

struct Message: Decodable {
    
    var affenpinscher: [String:[String]]?
    var african: [String]?
    var airedale: [String]?
    var akita: [String]?
    var appenzeller: [String]?
    var australian: [String]?
    var basenji: [String]?
}

As you can see in the first value I was trying to play with data types, but no success.

I am decoding and parsing JSON here:

class ContentModel: ObservableObject {
    
    @Published var dogs = Message()
    
    init() {
        getDogs()
    }
    
    func getDogs(){
        
        // Create URL
        let urlString = Constants.apiUrl
        let url = URL(string: urlString)
        
        if let url = url {
            // Create URL request
            var request = URLRequest(url: url, cachePolicy: .reloadIgnoringLocalCacheData, timeoutInterval: 10)
            request.httpMethod = "GET"
             
            // Get URLSession
            let session = URLSession.shared
            
            // Create Data Task
            let dataTask = session.dataTask(with: request) { (data, response, error) in
                // Check that there is not an error
                if error == nil {
                    
                    do {
                        // Parse JSON
                        let decoder = JSONDecoder()
                        let result = try decoder.decode(Dog.self, from: data!)
                        print(result)
                        
                        // Assign result to the dogs property
                        DispatchQueue.main.async {
                            self.dogs = result.message!
                        }
                    } catch {
                        print(error)
                    }
                }
            }
            
            // Start the Data Task
            dataTask.resume()
        }
    }
    
}

And here I would love to iterate through it eventually, which I also have no idea how to do it:

struct ContentView: View {
    
    @EnvironmentObject var model: ContentModel
    
    var body: some View {
        NavigationView {
            ScrollView {
                LazyVStack {
                    if model.dogs != nil {
//                        ForEach(Array(model.dogs.keys), id: \.self) { d in
//                            Text(d)
//                        }
                    }
                }
                .navigationTitle("All Dogs")
            }
            
        }
    }
}

What can I try next to resolve this?

Don’t make properties optional by default, only make them that if they actually can be nil. And we can’t really help you with how Message should be declared since it’s content isn’t clear from the given json. — Joakim Danielson
– Joakim Danielson, Commented Feb 12, 2022 at 18:41
If we assume that in message that the values for each key is a string array then I wouldn’t create separate properties but just decode the whole message as a dictionary, let message: [String: [String]] (in Dogs) and then convert it into something more useful in a later step — Joakim Danielson
– Joakim Danielson, Commented Feb 12, 2022 at 18:52
Hi @JoakimDanielson, to your first comment. when I put the api url to website I can see something like this: "message": "australian": 0: "sheppard" I will post a screenshot as well in my question above, so it is more clear what I mean. To your second comment. I think that is a good idea too. I can try that too! — Peter Mihok
– Peter Mihok, Commented Feb 12, 2022 at 18:58
@JoakimDanielson also when I make message:[String:[String]] then in my ContentModel.swift in DispatchQueue where I am assigning self.dogs = result.message! now I should I have self.dog = [result:result.message!] ? Because this is confusing me a lot! — Peter Mihok
– Peter Mihok, Commented Feb 12, 2022 at 19:10

vadian · Accepted Answer · 2022-02-12 19:49:33Z

2

First of all don't use classes for a JSON model and to conform to Identifiable you have to add an id property and CodingKeys if there is no key id in the JSON.

My suggestion is to map the unhandy [String: [String]] dictionary to an array of an extra struct

I renamed Dog as Response and named the extra struct Dog

struct Dog {
    let name : String
    let types : [String]
}

struct Response: Decodable, Identifiable {
    
    private enum CodingKeys: String, CodingKey { case message, status }
    let id = UUID()
    
    let dogs: [Dog]
    let status: String
    
    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        status = try container.decode(String.self, forKey: .status)
        let message = try container.decode([String:[String]].self, forKey: .message)
        dogs = message.map(Dog.init).sorted{$0.name < $1.name}
    }
}

In the model declare

@Published var dogs = [Dog]()

and decode

let result = try decoder.decode(Response.self, from: data!)
print(result)

// Assign result to the dogs property
DispatchQueue.main.async {
    self.dogs = result.dogs
}

The dogs array can be displayed seamlessly in a List

PS: Actually appenzeller is supposed to be

"appenzeller": ["sennenhund"],

or correctly in English

 "appenzell": ["mountain dog"],

😉😉😉

edited Feb 12, 2022 at 19:49

answered Feb 12, 2022 at 19:32

vadian

286k32 gold badges378 silver badges379 bronze badges

Sign up to request clarification or add additional context in comments.

14 Comments

Peter Mihok Over a year ago

Thanks Vadian, It helps a lot. It is very different approach and very experienced for me haha. I will need to study what you did there for couple of hours I guess...but I am getting no errors now and it prints into console all the dogs now. Now, I just need to print them in my UI somehow :O Is there any different way how to display them in the List?

vadian Over a year ago

You don't need if model.dogs != nil because the array is non-optional. Delete the if expression. Just iterate the array and display ForEach(model.dogs) { dog in Text(dog.name)

Peter Mihok Over a year ago

Yes, I figure that out! Hmm, I can see the dog names in the console, but not in the UI, haha. So, weird.

Peter Mihok Over a year ago

Fixed it! There was a problem in my List. THanks a lot!

vadian Over a year ago

I'm sorry, I don't support this inefficient dictionary way. Please take my suggestion or leave it.

|

Jordan Ellis · Accepted Answer · 2022-02-12 20:29:39Z

Using the native Swift approach that @vadian answered is a much lighter weight solution, but if you work with JSON often I'd recommend using SwiftyJSON.

You can parse the URL data task response into a Swifty json object like so:

import SwiftyJSON

guard let data = data, let json = try? JSON(data: data) else {
    return
}

// Make sure the json fetch was successful 
if json["status"].stringValue != "success" {
   return
}

Then you can access the message object safely without the verbosity of using Decodable. Here the message is parsed into an array of dog structs:

struct Dog {
    let name : String
    let types : [String]
}

var dogs: [Dog] = []

/// Load the docs into an array
for (name, typesJson) in json["message"].dictionaryValue {
    dogs.append(Dog(name: name, types: typesJson.arrayValue.map { $0.stringValue }))
}

print("dogs", dogs)

Collectives™ on Stack Overflow

SwiftUI decoding JSON from API

2 Answers 2

14 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

14 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related