使用Realm解码嵌套非数组Object时映射失败问题求助

Hey there, let's get this decoding issue sorted out right away! The root problem here is a mismatch between your JSON structure and how you're trying to decode it:

• Your JSON has a single kitchens object ({ "id": 36, "name": "Sandwiches" }), but your code is trying to decode it as an array of VendorKitchens using [VendorKitchens].self. That's exactly why you're hitting the "Failed to map data to JSON" error.

Here's how to fix it step by step: #

1. Update the VendorsList model property

Replace the List<VendorKitchens> with a single optional VendorKitchens object—since your JSON returns one kitchen entry, not a list:

class VendorsList : Object, Decodable {
    @objc dynamic var id : Int = 0
    @objc dynamic var name : String?
    @objc dynamic var logo : String?
    // Swap List for a single object to match JSON structure
    @objc dynamic var kitchens: VendorKitchens?

    override class func primaryKey() -> String? {
        return "id"
    }

    private enum CodingKeys: String, CodingKey {
        case id
        case name
        case logo
        // Match the JSON key directly instead of renaming it
        case kitchens
    }

2. Fix the decoder initialization logic

Instead of trying to decode an array, decode the single VendorKitchens object. Update the init(from decoder:) method:

public required convenience init(from decoder: Decoder) throws {
        self.init()
        let container = try decoder.container(keyedBy: CodingKeys.self)
        self.id = try container.decode(Int.self, forKey: .id)
        // Use decodeIfPresent for optional string values to avoid crashes if keys are missing
        self.name = try container.decodeIfPresent(String.self, forKey: .name)
        self.logo = try container.decodeIfPresent(String.self, forKey: .logo)
        // Decode the single kitchens object instead of forcing it into an array
        self.kitchens = try container.decodeIfPresent(VendorKitchens.self, forKey: .kitchens)
    }
}

3. Keep your VendorKitchens model as is

Your existing VendorKitchens class is already set up correctly for decoding a single object, so no changes needed here:

class VendorKitchens : Object, Decodable {
    @objc dynamic var id : Int = 0
    @objc dynamic var name : String?

    override class func primaryKey() -> String? {
        return "id"
    }

    private enum CodingKeys: String, CodingKey {
        case id
        case name
    }
}

Why this works: #

• We've aligned the model property type (VendorKitchens?) with the actual JSON structure (a single object instead of an array).
• The decoder now correctly tries to parse a single VendorKitchens instance from the kitchens key, instead of forcing it into an array which doesn't match the data.

If later your API starts returning an array of kitchens (like "kitchens": [{...}, {...}]), you can switch back to using List<VendorKitchens> and decode it as an array again. But for your current JSON, this setup will resolve the decoding error.

内容的提问来源于stack exchange，提问作者King