Null values decoding works well with Codable protocol, but when I have JSON that has NaN, everything crashes, how do I solve this?

I have spent last couple days, but did not find a solution.

Say, we have following code:

[
{
        "id": 1
        "apples": 193,
        "oranges": NaN,
        "bananas": null,
        "pineapples": 405,
        "watermelons": 13
        "comment": "oranges and bananas have invalid values"
}
]

And this struct:

struct Fruits: Codable, Identifiable {
    var id: Int
    var apples: Int?
    var oranges: Int?
    var bananas: Int?
    var pineapples: Int?
    var watermelons: Int?
    var comment: String?
}

How to decode this with no crashes?

CodePudding user response：

Use decode if present As we know oranges is integer type

import Foundation
struct Fruits : Codable, Identifiable {
    let id : Int?
    let apples : Int?
    let oranges : Int?
    let bananas : Int?
    let pineapples : Int?
    let watermelons : Int?
    let comment : String?

    enum CodingKeys: String, CodingKey {

        case id = "id"
        case apples = "apples"
        case oranges = "oranges"
        case bananas = "bananas"
        case pineapples = "pineapples"
        case watermelons = "watermelons"
        case comment = "comment"
    }

    init(from decoder: Decoder) throws {
        let values = try decoder.container(keyedBy: CodingKeys.self)
        id = try values.decodeIfPresent(Int.self, forKey: .id)
        apples = try values.decodeIfPresent(Int.self, forKey: .apples)
        oranges = try values.decodeIfPresent(Int.self, forKey: .oranges)
        bananas = try values.decodeIfPresent(Int.self, forKey: .bananas)
        pineapples = try values.decodeIfPresent(Int.self, forKey: .pineapples)
        watermelons = try values.decodeIfPresent(Int.self, forKey: .watermelons)
        comment = try values.decodeIfPresent(String.self, forKey: .comment)
    }

}

if there is some value against fruits between 0 to n then it will show the value otherwise it will return nil so you can easily achieve

CodePudding user response：

since your data is not valid json, you could try this approach where the original data is made into valid json, works very well for me.

Note: you are also missing a comma after id and watermelons

struct ContentView: View {
    
    var body: some View {
        Text("testing")
            .onAppear{
                let json = """
[
{
        "id": 1,
        "apples": 193,
        "oranges": NaN,
        "bananas": null,
        "pineapples": 405,
        "watermelons": 13,
        "comment": "oranges and bananas have invalid values"
}
]
"""
                // simulated api data
                let data = json.data(using: .utf8)!
                
                // convert to string
                let jsString = String(data: data, encoding: .utf8)!
                // convert back to data after replacements
                let newData = jsString.replacingOccurrences(of: "NaN", with: "null").data(using: .utf8)!
                
                do {
                    let fruits = try JSONDecoder().decode([Fruits].self, from: newData)
                    print("\n---> fruits: \(fruits)")
                } catch (let error) {
                    print("\n---> error: \(error)")
                }
            }
    }
}