Convert Swift Encodable class typed as Any to dictionary

Question

In connection with my previous questions, I decided to subclass NSArrayController in order to achieve the desired behavior.

class NSPresetArrayContr         


        

Answer 1

The type of the value that you pass to encode(_:) has to be a concrete type that implements Encodable. This means you need to recover the object's real type from the Any that you have. In order to cast, you must have a statically-specified type to which you are casting. You can't say object as! type(of: object), in other words; you have to say object as? MyClass (or in a generic context you can say object as? T).

Therefore, I believe that the only way to get around this is to statically enumerate the types you are working with, like so:

import Foundation

struct S : Encodable {
    let i: Int
}

struct T : Encodable {
    let f: Float
}

struct U : Encodable {
    let b: Bool
}

func plistObject(from encodable: Any) -> Any? {
    let encoded: Data?
    switch encodable {
        case let s as S:
            encoded = try? PropertyListEncoder().encode(s)
        case let t as T:
            encoded = try? PropertyListEncoder().encode(t)
        case let u as U:
            encoded = try? PropertyListEncoder().encode(u)
        default:
            encoded = nil
    }

    guard let data = encoded else { return nil }

    return try? PropertyListSerialization.propertyList(from: data,
                                                       options: [],
                                                       format: nil)
}

Needless to say, this is rather gross. It's inflexible, repetitive boilerplate. I'm not sure I can actually recommend its use. It's an answer to the literal question, not necessarily a solution to the problem.