CODEWITHSUNDEEP
swiftclasscodable
claes
claes

Reputation: 86

SwiftUI adding Codable conformance for @Published properties using 'id' property

I'm just starting out on learning SwiftUI. Where do I go wrong? I'm trying to add Codable conformance in my class (ManyItems). This so I eventually can save an array to disk using JSON. Two errors:

1) In both the "required init(...) "id = try..." and the encode func: "try container.encode..." result in "'id' is unavailable in Swift: 'id' is not available in Swift; use 'Any'"

2) In both the required init(...) and func encode: "Use of unresolved identifier 'one'." I assumed the identifier in the struct would be carried forward into the class?

struct Item: Identifiable {
    var id = UUID()
    var one: String
}

class ManyItems: ObservableObject, Codable {
    @Published var manyitems = [Item]()
    enum CodingKeys: CodingKey {
        case id
        case one
    }
    required init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        id = try container.decode(UUID.self, forKey: .id)
        one = try container.decode(String.self, forKey: .one)
    }
    func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)
        try container.encode(id, forKey: .id)
        try container.encode(one, forKey: .one)
    }
}

Upvotes: 2

Views: 1948

Answers (2)

claes
claes

Reputation: 86

I've found a solution but had to take a slightly different route. Hopefully this could help someone else who needs to use a Collection conforming to Codable and ObservableObject for saving to the Apps documentDirectory.

I conformed the struct 'Item' to Codable (i.e not the class 'ManyItem'). I added code for JSON encoding and saving of the Collection to the Apps documentDirectory. This happens automatic when a property value changes. The class is initiated through either a read/decoding of the JSON file from the Apps document directory or as a new blank instance if the JSON file is not available yet. 

struct Item: Identifiable, Codable {
    var id = UUID()
    var one: String    
}

class ManyItems: ObservableObject {
    @Published var manyitems: [Item] {
        didSet {
            // Saves the array 'items' to disc
            do {
                // find the documentDirectory and create an URL for the JSON
                file
                let filename = getDocumentsDirectory().appendingPathComponent("manyitems.json")
            let data = try JSONEncoder().encode(self.manyitems)
            try data.write(to: filename, options: [.atomicWrite])
        } catch {
            print("Unable to save data.")
        }
    }
}
init() {
    // replaces a call to 'getDocumentsDirectory()' methode as it created an initialisation error.
    let paths = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
    // Add the first [0] path to the filename and create 'filename'
    let filename = paths[0].appendingPathComponent("manyitems.json")
    //print(filename)
    do {
        // Try to read the file (if it exist) and load the data into the array 'manyitem'
        let data = try Data(contentsOf: filename)
        manyitems = try JSONDecoder().decode([Item].self, from: data)
        // Yes all good then exit
        return
    } catch {
        // Something whent wrong. Initialize by creating an empty array 'manyitems'
        self.manyitems = []
        print("Unable to load saved data.")
    }
}
// retreives the App's first DocumentDirectory
func getDocumentsDirectory() -> URL {
    let paths = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
    return paths[0]
}

}

Upvotes: 0

PGDev
PGDev

Reputation: 24341

Your Codable models should be,

struct Item: Codable, Identifiable {
    var id = UUID()
    var one: String
}

class ManyItems: Codable, ObservableObject {
    @Published var manyitems = [Item]()
}

As evident from your code, you're not handling any specific parsing cases. So, there is no need to explicitly implement init(from:) and encode(to:) methods.

Upvotes: -1

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