protocolequatable.swift

//: Playground - noun: a place where people can play

import UIKit

protocol AccountLike: Equatable {
    var accountID: String {get}
}

class Account : AccountLike {
    let accountID = nil
}

// https://twitter.com/optshiftk/status/628985834801336320

func ==<T: AccountLike>(lhs: T, rhs: T) -> Bool {
    return lhs.accountID == rhs.accountID
}

class FooAccount: Account {
    
    let accountID = "foo"
}

class BarAccount: Account {
    
    let accountID = "bar"
}

let foo = FooAccount()
let bar = BarAccount()
var accounts: [Account] = [Account]()