Equatable Type Erasure

Equating.swift

protocol Equating {
    func isEqualTo(_ other: Equating)-> Bool
}

extension Equating where Self: Equatable {
    func isEqualTo(_ other: Equating) -> Bool {
        guard let other = other as? Self else { return false }
        return other == self
    }
}

/* Examples */

struct Person: Equating & Equatable {
    let name: String
    let age: Int
}

struct Favourites: Equating & Equatable {
    let color: UIColor
    var person: Person? = nil
}

extension Favourites {
    init(color: UIColor, person: Person) {
        self.color = color
        self.person = person
    }
}

Person(name: "fred", age: 22).isEqualTo(Person(name: "Frank", age: 33))
Person(name: "fred", age: 22).isEqualTo(Person(name: "fred", age: 22))
Person(name: "fred", age: 22).isEqualTo(Favourites(color: .red))
Favourites(color: .black, person: Person(name: "x", age: 12)).isEqualTo(Favourites(color: .black))
Favourites(color: .black, person: Person(name: "x", age: 12)).isEqualTo(Favourites(color: .black, person: Person(name: "x", age: 12)))
Favourites(color: .green).isEqualTo(Favourites(color: .black))

let examples: [Equating] = [
    Person(name: "fred", age: 22),
    Person(name: "Frank", age: 33),
    Favourites(color: .red),
    Favourites(color: .red)
]

for idx in 1..<examples.count {
    let result = examples[idx-1].isEqualTo(examples[idx])
    print(result)
}