This MyError Helper can help us to build a concrete Errors in Swift

MyError.swift

/* Error Handling in Swift*/

struct MyError: Error {
    private let possibleErrors: [Int:String] = {
        return [
            200: "Success",
            403: "Forbidden",
            404: "Not Found",
            500: "Internal Server Error",
            -999: "Make use of this Error code with your own usage"]
    }()
    let domain: String
    let code: Int
    let userInfo: [String: Any]?
    
    init(domain: String = "com.example", code: Int, userInfo: [String: Any]?) {
        self.domain = domain
        self.code = code
        self.userInfo = userInfo
    }
    var localizedDescription: String {
        if let desc = userInfo?[NSLocalizedDescriptionKey] {
            return desc as! String
        }
        return possibleErrors[code] ?? "Internet Failure"
    }
}

extension MyError {
    static func error(with nsError: NSError) -> MyError {
        return MyError(domain: nsError.domain, code: nsError.code, userInfo: nsError.userInfo)
    }
}