Ptbaileys / CodableNilOnFail

Easy failable optional enum properties in Swift Codable.

CodableNilOnFail

Easy failable optional enum properties in Swift Codable.

Installation

You can add CodableNilOnFail to an Xcode project by adding it as a package dependency.

1. From the File menu, select Add Packages…
2. Enter https://github.com/sochalewski/CodableNilOnFail into the package repository URL text field.
3. Add the package to your app target.

Why?

Consider the following data model:

struct Car: Codable {
    enum Manufacturer: String, Codable {
        case toyota, volkswagen, ford, honda, generalMotors
    }
    
    var manufacturer: Manufacturer?
    var vin: String?
    var owner: String?
}

Everything works perfectly if the received JSON matches the available Manufacturer enum values, like this:

{
    "manufacturer": "toyota",
    "vin": "JT4RN67S0G0002845",
    "owner": null
}

But Car.manufacturer is optional, so it makes sense to have a valid model, even if the received manufacturer doesn't match one of the currently supported ones:

{
    "manufacturer": "tesla",
    "vin": "5YJSA2DP8DFP22249",
    "owner": "Elon Musk"
}

Unfortunately decoding this with JSONDecoder results in getting nil for the whole Car instead of just Car.manufacturer.

This can be solved by custom init(from:) of the Decodable protocol, but that's a lot of boilerplate, especially when you have dozens of enums in your models.

This is where CodableNilOnFail comes in!

Usage

Just add the @NilOnFail property wrapper to your optional RawRepresentable properties.

struct Car: Codable, Equatable {
    enum Manufacturer: String, Codable {
        case toyota, volkswagen, ford, honda, generalMotors
    }
    
    @NilOnFail var manufacturer: Manufacturer?
    var vin: String?
    var owner: String?
}

Author

Piotr Sochalewski, sochalewski.github.io