medium-form-combine-LoginViewModel.swift

//
//  LoginViewModel.swift
//

import Combine
import Foundation

// 1
class LoginViewModel: ObservableObject {
    // 2
    enum ViewState {
        case loading
        case success
        case failed
        case none
    }
    // 3
    @Published var email = ""
    @Published var password = ""
    @Published var state: ViewState = .none
    // 4
    var isValidUsernamePublisher: AnyPublisher<Bool, Never> {
        $email
            .map { $0.isValidEmail }
            .eraseToAnyPublisher()
    }

    var isValidPasswordPublisher: AnyPublisher<Bool, Never> {
        $password
            .map { !$0.isEmpty }
            .eraseToAnyPublisher()
    }
    // 5
    var isSubmitEnabled: AnyPublisher<Bool, Never> {
        Publishers.CombineLatest(isValidUsernamePublisher, isValidPasswordPublisher)
            .map { $0 && $1 }
            .eraseToAnyPublisher()
    }
    // 6
    func submitLogin() {
        state = .loading
        // hardcoded 2 seconds delay, to simulate request
        DispatchQueue.main.asyncAfter(deadline: .now() + .seconds(2)) { [weak self] in
            guard let self = self else { return }
            // 7
            if self.isCorrectLogin() {
                self.state = .success
            } else {
                self.state = .failed
            }
        }
    }
    
    func isCorrectLogin() -> Bool {
        // hardcoded example
        return email == "[email protected]" && password == "12345"
    }
}

extension String {
    // 8
    var isValidEmail: Bool {
        return NSPredicate(
            format: "SELF MATCHES %@", "[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,}"
        )
        .evaluate(with: self)
    }
}