How to make JSON from an Encodable of an arbitrary class?

Question

Swift

There is a function in Swift 4:

func encode(item: Encodable) -> Data {
        return JSONEncoder().encode(item)
}

But the compiler throws an error

Protocol type 'Encodable' cannot conform to 'Encodable' because only concrete types can conform to protocols

How to implement similar functionality without using concrete classes?

Answer 1

Yes, there is no method in Encoder that would accept an abstract Encodable, it needs a concrete type. Generics will help to achieve this by virtue of their implementation.

func encode<T: Encodable>(_ item: T) throws -> Data {
    return try JSONEncoder().encode(item)
}