Convert null values to default strings in parsing JSON using JSONDecoder in Swift

Question

I am trying to parse some JSON in Swift using JSONDecoder where the JSON occasionally has null values. I would like to put in a default instead. The following allows me to handle it but the nulls cause problems later.

struct Book: Codable {
        let title : String
        let author: String?
    }

Is there a way to do something like (following does not compile), perhaps using an initializer?:

struct Book: Codable {
        let title : String
        let author: String ?? "unknown"
    }

Thanks for any suggestions

Answer 1

This could be address by manually decoding as described here.

The other way to go would be to have the stored properties reflect the data exactly, and then have a computed var for the case of providing a non-optional value.

struct Book: Codable {
    let title : String
    let author: String?

    var displayAuthor: String {
        return author ?? "unknown"
    }
}

The other reason this might be appealing is it preserves the optional value should you need to check if the value exists at all in the future.