Swift Type Erasure Example

TypeErasureExample.swift

import UIKit

protocol Decodable {
    func decode() -> Void
}

struct Action {
    let decodable: AnyDecodable
}

protocol Requestable {
    func perform(action: Action)
}

struct AnyDecodable: Decodable {
    let _decode: () -> Void
    
    init<D: Decodable>(_ decodable: D) {
        _decode = decodable.decode
    }
    
    func decode() {
        _decode()
    }
}

extension String: Decodable {
    func decode() { print(self) }
}

let s = "hello"
let erased = AnyDecodable(s)
erased.decode()


class MockRequestable: Requestable {
    var action: Action!
    
    init() {}
    
    func perform(action: Action) {
        self.action = action
    }
}