Decoding JSON SwifUI

Question

Jad-T OP

Created Dec ’20

Replies 10

Boosts 0

Views 3.4k

Participants 3

Hello
I'm trying to decode a JSON File but it's not working and I can't understand why

Code:

Code Block 
import SwiftUI
struct Search: View {
    
    let sf: [SF] = Bundle.main.decode("sf.json")
    @State private var searchText: String = ""
    var body: some View {
        NavigationView{
            Form {
                Section(header: Text("Search bar")){
                TextField("Search", text: $searchText)
                    .padding(7)
                    .background(Color(.systemGray6))
                    .cornerRadius(8)
                }
                Section(){
                    List{
                        ForEach(sf) { item in
                            Text(item.title)
                        }
                    }
                }
            }
            .navigationTitle("SF")
        }
    }
    
}
struct SF: Codable, Identifiable {
    var id: String
    var title: String
    var items: [String]
}
extension Bundle {
  func decode<T: Codable>(_ file: String) -> T {
    
    guard let url = self.url(forResource: file, withExtension: nil) else {
      fatalError("Failed to locate \(file) in bundle.")
    }
    
    
    guard let data = try? Data(contentsOf: url) else {
      fatalError("Failed to load \(file) from bundle.")
    }
    
    
    let decoder = JSONDecoder()
    
   
    guard let loaded = try? decoder.decode(T.self, from: data) else {
      fatalError("Failed to decode \(file) from bundle.")
    }
    
   
    return loaded
  }
}

Here is the JSON file

Code Block [
  {
    "id": "all"
    "title": "All",
    "items": [
      "square.and.arrow.up",
      "square.and.arrow.up.fill",
      "square.and.arrow.down"
      ]
   }
]

Thank you

Answered by OOPer in 654447022

This is the file now:

Apparently, it does not have "id" in any elements.

You can remove id as a stored property from SF to make your file decodable,
and add another computed property id to make it conform to Identifiable:

Code Block struct SF: Codable, Identifiable {
    //var id: String //<- Remove this stored property
    var id: String {title} //<- Add this computed property
    var title: String
    var items: [String]
}

And I have another question about the decimalPad

That is not for this thread. Please keep, one thread for one topic.

Boost

Answer 1

Claude31 OP

Dec ’20

I'm trying to decode a JSON File but it's not working and I can't understand why

It is not working is not an information.

what do you get ? Is it a wrong result (which) or no result at all ? (what do you get in loaded ?
Does it crash ? If so, what is the crash log

I looked at the code:
Isn't there a comma missing at the end of line 5 in JSON file ?

Note: when you paste code, use Paste and Match Style, to avoid the extra blank lines that make code quasi impossible to analyse.

Code Block import SwiftUI
struct Search: View {
    
    let sf: [SF] = Bundle.main.decode("sf.json")
    @State private var searchText: String = ""
    var body: some View {
        NavigationView{
            Form {
                Section(header: Text("Search bar")){
                TextField("Search", text: $searchText)
                    .padding(7)
                    .background(Color(.systemGray6))
                    .cornerRadius(8)
                }
                Section(){
                    List{
                        ForEach(sf) { item in
                            Text(item.title)
                        }
                    }
                }
            }
            .navigationTitle("SF")
        }
    }
    
}
struct SF: Codable, Identifiable {
    var id: String
    var title: String
    var items: [String]
}
extension Bundle {
  func decode<T: Codable>(_ file: String) -> T {
    
    guard let url = self.url(forResource: file, withExtension: nil) else {
      fatalError("Failed to locate \(file) in bundle.")
    }
    
    guard let data = try? Data(contentsOf: url) else {
      fatalError("Failed to load \(file) from bundle.")
    }
    
    let decoder = JSONDecoder()
   
    guard let loaded = try? decoder.decode(T.self, from: data) else {
      fatalError("Failed to decode \(file) from bundle.")
    }
    
      return loaded
  }
}

0

Answer 2

Jad-T OP

Dec ’20

I tried putting the comma but it's not working anyway, it gives me a fatalError("Failed to decode \(file) from bundle.")

0

Answer 3

Jad-T OP

Dec ’20

Actually now it worked but I changed the JSON file (you can find it by searching SF Symbols JSON, I pasted the JSON file in my project) and it stopped working again.

0

Answer 4

OOPer OP

Dec ’20

I recommend NEVER to use try?, which throws away all the error info.

Change your line 79...83 as:

Code Block     let data: Data
    do {
        data = try Data(contentsOf: url) //<-`try`, not `try?`
    } catch {
        fatalError("Failed to load \(file) from bundle.: \(error)")
    }

And line 95...99:

Code Block         let loaded: T
        do {
            loaded = try decoder.decode(T.self, from: data) //<-`try`, not `try?`
        } catch {
            fatalError("Failed to decode \(file) from bundle.: \(error)")
        }

And please tell us what you get. That would show some info where to fix.

0

Answer 5

Jad-T OP

Dec ’20

Hello
I tried your solution and got this:
Thread 1: Fatal error: Failed to decode sf.json from bundle.: keyNotFound(CodingKeys(stringValue: "id", intValue: nil), Swift.DecodingError.Context(codingPath: [_JSONKey(stringValue: "Index 0", intValue: 0)], debugDescription: "No value associated with key CodingKeys(stringValue: \"id\", intValue: nil) (\"id\").", underlyingError: nil))

0

Answer 6

OOPer OP

Dec ’20

got this:

Code Block Thread 1: Fatal error: Failed to decode sf.json from bundle.: keyNotFound(CodingKeys(stringValue: "id", intValue: nil), Swift.DecodingError.Context(codingPath: [_JSONKey(stringValue: "Index 0", intValue: 0)], debugDescription: "No value associated with key CodingKeys(stringValue: \"id\", intValue: nil) (\"id\").", underlyingError: nil))

Thanks for trying. And the most important part of the error is: keyNotFound and "id".
It represents your sf.json lacks "id" in the first element of the JSON array.

I have tested your code (including my suggestions) with this sf.json and it worked without runtime errors.
sf.json:

Code Block [
  {
    "id": "all",
    "title": "All",
    "items": [
      "square.and.arrow.up",
      "square.and.arrow.up.fill",
      "square.and.arrow.down"
      ]
   }
]

(I filled comma at the end of Line 3, as you see.)

What is your current sf.json? Does it have an entry for "id"?

0

Answer 7

Jad-T OP

Dec ’20

This is the file now:
[

{

"title": "Shapes",

"items": [

"rectangle",

"rectangle.fill",

"shield",

"shield.fill"

]

},

{

"title": "Arrows",

"items": [

"arrowshape.turn.up.left",

"arrowshape.turn.up.left.fill",

"arrowshape.turn.up.left.circle",

"arrowshape.turn.up.left.circle.fill"

]

}

]

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Answer 8

Jad-T OP

Dec ’20

Hello
And I have another question about the decimalPad

Code Block     @State var deci = 3
     var numberFormatter: NumberFormatter = {
         let nf = NumberFormatter()
         nf.locale = Locale.current
         nf.numberStyle = .decimal
         nf.maximumFractionDigits = deci
         return nf
     }()

How do I fix this at line 10:
Instance member 'deci' cannot be used on type 'BMIView'; did you mean to use a value of this type instead?

Thank you very much for your time

0

Answer 9

OOPer OP

Dec ’20

Accepted Answer

This is the file now:

Apparently, it does not have "id" in any elements.

You can remove id as a stored property from SF to make your file decodable,
and add another computed property id to make it conform to Identifiable:

Code Block struct SF: Codable, Identifiable {
    //var id: String //<- Remove this stored property
    var id: String {title} //<- Add this computed property
    var title: String
    var items: [String]
}

And I have another question about the decimalPad

That is not for this thread. Please keep, one thread for one topic.

1

Answer 10

Jad-T OP

Dec ’20

It worked thank you

0