Basic == overloading fails - ios

Question

My desired end result is to be able to compare to [Server] objects for equality, like so:
let server1 = Server(username: "1")
let server2 = Server(username: "2")
let server1Array = [server1]
let server2Array = [server2]
print(server1Array == server2Array)
I have a class called Server, and I want to overload the == for arrays of Server:
// Server.swift
import Foundation
infix operator ==: AssignmentPrecedence
class Server: ServerRepresentable {
let username: String
init(username: String) {
self.username = username
}
}
// This protocol's only purpose is to allow me to use the `where` clause in the extension below
protocol ServerRepresentable {
var username: String { get }
}
extension Array where Element: ServerRepresentable {
static func == (lhs: Array<ServerRepresentable>, rhs: Array<ServerRepresentable>) {
let server1Usernames = lhs.map { $0.username }
let server2Usernames = rhs.map { $0.username }
// ERROR: Cannot convert value of type '[String]' to expected argument type 'Bool'
return server1Usernames == server2Usernames
}
}
As you can see, I get the error "Cannot convert value of type '[String]' to expected argument type 'Bool'" when I try to perform server1Usernames == server2Usernames, which are both arrays of strings. This is strange because the == operator should already come overloaded in [String] comparisons.
What gives? Is the compiler getting confused because I'm overloading the operator in this class?

Answer 1

There is no need to extend Array. Just make sure your Server conforms to Equatable protocol:
class Server: ServerRepresentable, Equatable {
let username: String
init(username: String) {
self.username = username
}
static func == (lhs: Server, rhs: Server) -> Bool {
lhs.username == rhs.username
}
}
let server1 = Server(username: "1")
let server2 = Server(username: "2")
let server1Array = [server1]
let server2Array = [server2]
print(server1Array == server2Array) // "false\n"
Regarding your question you forgot to add a returning type Bool but the error displayed by the code you have posted should be Unexpected non-void return value in void function

Answer 2

This only works for string, int, double, float arrays.
You could try something like this
To check if there is a difference
for server1 in servers1 {
var name1 = [String]()
var name2 = String()
for server2 in servers2 {name1.append(server2.name)}
name2 = server1.name
if name1.contains(name2) {
print("found duplication")
}
To find the differences
for server1 in servers1 {
var name1 = [String]()
var name2 = String()
for server2 in servers2 {name1.append(server2.name)}
name2 = server1.name
print(name1. difference(name2))
}
//
extension Array where Element: Hashable {
func difference(from other: [Element]) -> [Element] {
let thisSet = Set(self)
let otherSet = Set(other)
return Array(thisSet.symmetricDifference(otherSet))
}
}