Json not loading in SwiftUI

Question

am trying to load this json into my swiftui app

 {
            "id": "EF1CC5BB-4785-4M8E-AB98-5FA4E00B6A66",
            "name" : "opening the box",
            "group" : [
            
            {
                "name" : "Open  box",
                "windows" : "Double-click",
                "mac" : "right-click"
                
            },
            {
                "name" : "Duplicate",
                "windows" : "right click and choose from options",
                "mac" : "option + drag"
                
            }
            
            
            
            
            ]
        },

and there are many more elements like this

and here are the structs that I made

struct topic: Codable, Identifiable {
    
    var id: UUID
    var name: String
    var group: [shortcuts]
    
    
}

struct shortcuts: Codable, Equatable, Identifiable{
    
    var id = UUID()
    var name: String
    var windows: String
    var mac: String

}

and here is the code for decoding it

import UIKit

extension Bundle {
    
    func decode<T: Decodable>(_ type: T.Type, from file: String) -> T {
        
        guard let url = self.url(forResource: file, withExtension: nil) else {
            
            fatalError("failed")
      
        }
        
        guard let data = try? Data(contentsOf: url) else {
            
            
            fatalError("failed to do it")
            
        }
        
        let decoder = JSONDecoder()
        
        guard let loaded = try? decoder.decode(T.self, from: data) else {
            fatalError("failed")
        }
        return loaded
        
    }
    
    
    
    
}

now when I create a constant like this inside my view

 let Topic = Bundle.main.decode([topic].self, from: "main.json")

and then I try to load the items like this

 NavigationView{
                List{
                    ForEach(Topic) { section in
                        Section(header: Text(section.name)) {
                            ForEach(section.group) { item in
                                shortcutRow(item: item)
                            }
                        }
                        
                        
     
                }
                
            }.navigationBarTitle("Menu")
             .listStyle(SidebarListStyle())
                
            
        }

it doesn't work it shows fatal error that is present in the second last line of code of my bundle extension that I created for decoding this json

please help

Your struct is not correct. Please, check this: https://stackoverflow.com/a/61483237/5941807 — Joannes, Oct 03 '21 at 06:42
" it shows fatal error that is present in the second last line of code of my " Don't do `fatalError` like that, Instead fo proper `do`/`try`/`catch` and print the caught `error` instead of `try?` because you are currently ignoring the error that could tell you exactly why it fails! — Larme, Oct 03 '21 at 06:50
See one a my previous answers on why use do/try/catch: https://stackoverflow.com/questions/69002011/swift-dispatch-queue-block-not-running/69002191#69002191 — Larme, Oct 03 '21 at 06:54

workingdog support Ukraine · Accepted Answer · 2021-10-03T09:34:46.923

1

"...and there are many more elements like this", that means the json you show is probably not the json you have. Most likely it is an array of what you show. Thus, in Bundle decode, you should decode and return [T] not T. Note you should use the normal convention of using uppercased name for types, such as Topic, and lowercased name for instances, topic. Given that, try this:

extension Bundle {
    
    // todo deal with errors
    func decode<T: Decodable>(from file: String) -> [T] {  // <-- here
        if let url = Bundle.main.url(forResource: file, withExtension: "json") {
            do {
                let data = try Data(contentsOf: url)
                let loaded = try JSONDecoder().decode([T].self, from: data)  // <-- here
                return loaded
            } catch {
                // todo deal with errors
                print("---> error: \(error)")
            }
        } else {
            // todo deal with errors
            print("---> error url: ")
        }
        return []
    }
    
}

struct Topic: Codable, Identifiable {
    var id, name: String
    var group: [Shortcuts]
}

struct Shortcuts: Codable, Identifiable {
    let id = UUID()  // <-- here use let
    var name, windows, mac: String
}

struct ContentView: View {
    let topics: [Topic] = Bundle.main.decode(from: "main") // <-- here
    
    var body: some View {
       Text("testing topics: \(topics.count)")
        .onAppear {
            print("---> topics: \(topics)")
        }
    }
}

EDIT:

This is the json data I used to test my answer:

[
{
           "id": "EF1CC5BB-4785-4M8E-AB98-5FA4E00B6A66",
           "name" : "opening the box",
           "group" : [
           {
               "name" : "Open  box",
               "windows" : "Double-click",
               "mac" : "right-click"
           },
           {
               "name" : "Duplicate",
               "windows" : "right click and choose from options",
               "mac" : "option + drag"
           }
           ]
       }
]

edited Oct 03 '21 at 09:34

answered Oct 03 '21 at 08:41

workingdog support Ukraine

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1

Please consider that the generic type `T` can be both a single object **and** an array depending on the passed parameter type. – vadian Oct 03 '21 at 08:47
yeah, sure, but I think it's easier to show it's an array. – workingdog support Ukraine Oct 03 '21 at 08:58
But the root object of the JSON is obviously a dictionary. The error occurs because there is no `id` key in `shortcuts` and no CodingKeys are specified to exclude `id`. – vadian Oct 03 '21 at 09:00
wrong, using `let id = UUID()` in `Shortcuts` will ensure id is not decoded. Even Xcode will tell you that much. I've tested my answer and set the json data as an array `[...]` as it probably should be in the first place. – workingdog support Ukraine Oct 03 '21 at 09:30
Of course but you get an ugly warning in Xcode. – vadian Oct 03 '21 at 09:35
@vadian, it's a shame you get an ugly warning. My Xcode for once, gives me a really helpful message telling me exactly what I need to know, on a beautiful yellow background. – workingdog support Ukraine Oct 03 '21 at 12:05
@workingdog how is sarcasm helpful? You should listen to the advices given to you because they could really improve your answer instead of passing on bad habits to less experienced programmers. – Joakim Danielson Oct 03 '21 at 13:47
1

point taken, it was meant as a joke, not to be taken seriously, apologies to all. – workingdog support Ukraine Oct 03 '21 at 22:56
Ok , I see. Maybe use a smiley next time. – Joakim Danielson Oct 04 '21 at 08:21
hey good idea, how do you do that? – workingdog support Ukraine Oct 04 '21 at 09:58
I meant the old fashioned one :) – Joakim Danielson Oct 04 '21 at 16:17
Emoji smilies are just text – vadian Oct 04 '21 at 19:04
Neat trick, bound to offend someone with these, – workingdog support Ukraine Oct 04 '21 at 23:02

Json not loading in SwiftUI

1 Answers1