Swift Error Handling: Authentication System - swift

Question

I am having problem displaying custom error message on Swift.
The scenario is basic user authentication with Dictionary data, input entered is validated with the Dictionary data, if username and password matches, return true, else an error message as "Invalid Credentials" with AuthenticationError appears (argument message CustomErrors enum)
Here is the code I have come up with so far:
import Foundation
//Editable code starts here
let authDict:Dictionary = ["admin":"admin123","user":"someone123","guest":"guest999","you":"yourpass","me":"mypass190"]
//create CustomErrors enum
public enum CustomErrors: Error {
case AuthenticationError(message:String)
//case invalidCredentials
}
extension CustomErrors: LocalizedError {
public var errorDescription: String? {
switch self{
//case .invalidCredentials:
// return NSLocalizedString("Invalid Credentials", comment: "Invalid Credentials")
//return "Invalid Credentials"
case .AuthenticationError(message:let message):
print(message)
return "Invalid Credentials"
}
}
}
// create authenticate(userName:user,pass:pass) with return type Boolean
func authenticate(user:String,pass:String) -> Bool{
print(user)
print(pass)
for(u,p) in authDict {
if((u == user) && (p == pass)) {
return true
}
}
print("Invalid Credentials")
return false
}
//Editable code ends here
//Uneditable code starts here
let stdout = ProcessInfo.processInfo.environment["OUTPUT_PATH"]!
FileManager.default.createFile(atPath: stdout, contents: nil, attributes: nil)
let fileHandle = FileHandle(forWritingAtPath: stdout)!
guard let user = readLine() else { fatalError("Bad input") }
guard let pass = readLine() else { fatalError("Bad input") }
do{
let result = try authenticate(user:user,pass:pass)
fileHandle.write((result ? "1" : "0").data(using: .utf8)!)
}catch CustomErrors.AuthenticationError(let message){
fileHandle.write(message.data(using: .utf8)!)
}
//Uneditable code ends here
The above code works perfect for all positive test cases like :
1. "admin":"admin123"
2. "user":"someone123"
3. "guest":"guest999"
4. "you":"yourpass"
5. "me":"mypass190"
The output is 1 for all above, but for negative test cases, I should get Invalid Credentials printed as output, instead I get 0
I am not sure what I am missing in the CustomErrors enum but its not working.
How do I fix my editable code to work with the below uneditable code, what should I add/delete to achieve the end result:
do{
let result = try authenticate(user:user,pass:pass)
fileHandle.write((result ? "1" : "0").data(using: .utf8)!)
}catch CustomErrors.AuthenticationError(let message){
fileHandle.write(message.data(using: .utf8)!)
}

Answer 1

Modify the authenticate function as:
func authenticate(user:String,pass:String) throws -> Bool{
print(user)
print(pass)
guard authDict[user] == pass else {
throw CustomErrors.AuthenticationError(message: "Invalid Credentials")
}
return true
}
Now the function throws a CustomErrors error if user and pass do not match those stored in the authDict Dictionary.