Question 108526 in IOS Swift Question posted in
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Ios swift – JSON file not load data

I have a problem with a JSON file the app crashes when it starts decoding and therefore the data is not loaded. I downloaded it from Facebook to test and I got the Facebook JSON file with all the friends in my account and the format is this:

{
  "friends_v2": [
    {
      "name": "Test Test",
      "timestamp": 1678361485
    },
    {
      "name": "Test2 ",
      "timestamp": 1678318229
    },
    {
      "name": "Test 3",
      "timestamp": 1675869376
    }
    ]
  }

As you can see the file doesn’t start with name and timestamp but before them there is "friends_v2". I noticed that if I delete that "friend_v2" everything works otherwise it doesn’t.

[
    {
      "name": "Test Test",
      "timestamp": 1678361485
    },
    {
      "name": "Test2 ",
      "timestamp": 1678318229
    },
    {
      "name": "Test 3",
      "timestamp": 1675869376
    }
  ]

In case I get uneditable JSON like this (so I can’t delete "friend_v2") how can I make everything work? Thank you very much for your time

This is my JSONManager.swift

struct Friends: Codable {
    var name: String
    var timestamp: Int
    var contact_info: String?

    
    static let allFriends: [Friends] = Bundle.main.decode(file: "friends.json")
    static let allFriendsSample: Friends = allFriends[0]
}

extension Bundle {
    func decode<T: Decodable>(file: String) -> T {
        guard let url = self.url(forResource: file, withExtension: nil) else {
            fatalError("Non è stato possibile trovare il file (file) nel progetto")
        }
        
        guard let data = try? Data(contentsOf: url) else {
            fatalError("Non è stato possibile caricare il file (file) nel progetto")
        }
                
        let decoder = JSONDecoder()
        
        guard let loadData = try? decoder.decode(T.self, from: data) else {
            
            fatalError("Non è stato possibile decodificare il file (file) nel progetto")
        }
        
        return loadData
    }
}

And I use in ContentView

struct ContentView: View {
    
    private var friends: [Friends] = Friends.allFriends
    
    var body: some View {
        VStack {
            List {
                ForEach(friends, id: .name) { friend in
                    Text(friend.name)
                }
            }
        }
        .padding()
    }
}
Tags:

3

Answers


  1. 0

    try this approach, using the following models.

    struct Friends: Codable {
    var name: String
    var timestamp: Int
    var contact_info: String?
 
    static let rootObj: RootObject = Bundle.main.decode(file: "friends.json")
    static let allFriends: [Friends] = rootObj.friendsV2

    static let allFriendsSample: Friends = allFriends[0]
}

struct RootObject: Codable {
    let friendsV2: [Friends]

    enum CodingKeys: String, CodingKey {
        case friendsV2 = "friends_v2"
    }
}
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  2. 0

    Since you are using fatalError, it means you are pretty sure about the errors.

    So instead: use try! instead of guard ... try? ... return { fatalError(...) }

    Then the compiler will tell you what is wrong with your code or the json

    ⚠️ Note that there is always a reason when a function is throwing and you should consider error handling instead of just silencing the compiler by using fatal.

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  3. 0

    Here’s an updated version of your Friends struct that includes a friends_v2 property that maps to the array in the JSON data:

    struct Friends: Codable {
    let friends_v2: [Friend]
    
    struct Friend: Codable {
        let name: String?
        let timestamp: Int?
        let contact_info: String?
    }
    
    static let allFriends: [Friend] = {
        guard let url = Bundle.main.url(forResource: "friends", withExtension: "json"),
              let data = try? Data(contentsOf: url),
              let friends = try? JSONDecoder().decode(Friends.self, from: data)
        else {
            fatalError("Unable to load friends from JSON file")
        }
        return friends.friends_v2
    }()
    
    static let allFriendsSample: Friend = allFriends[0]
}
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