mvvm_form_3.swift

mvvm_form_3.swift

final class ExampleViewModel: StateBindingViewModel<ExampleState> {
    // MARK: - Public Methods

    func performSignUp() {
        if state.password.count < 6 {
            state.passwordError = "The Password should have at least 6 characters."
        }
        // Do aditional validations and send the data to the server...
    }

    // MARK: - StateBindingViewModel Conformance

    override func stateWillChangeValue<Value>(
        _ keyPath: PartialKeyPath<ExampleState>,
        newValue: Value
    ) -> Bool where Value: Equatable {
        switch (keyPath, newValue) {
        case let (\ExampleState.password, newValue as String):
            state.passwordError = nil
            return newValue.count <= 12
        default:
            return true
        }
    }

    override func onStateChange(_ keyPath: PartialKeyPath<ExampleState>) {
        state.isSignUpButtonEnabled = isValidForm()
    }

    // MARK: - Private Methods

    private func isValidForm() -> Bool {
        return !state.email.isEmpty && !state.password.isEmpty
    }
}

struct ExampleView: View {
    // MARK: - Dependencies

    @StateObject var viewModel: ExampleViewModel

    // MARK: - View Content

    var body: some View {
        Form {
            Section(header: Text("E-mail")) {
                TextField(
                    "example@mail.com",
                    text: viewModel.binding(\.email)
                )
            }
            Section(header: Text("Password")) {
                SecureField(
                    "xxxxxx",
                    text: viewModel.binding(\.password)
                )
                if let passwordError = viewModel.state.passwordError {
                    Text(passwordError)
                        .font(.title3)
                        .foregroundColor(.red)
                }
            }
            Button(
                "Sign Up",
                action: viewModel.performSignUp
            )
            .disabled(viewModel.state.isSignUpButtonEnabled == false)
        }
    }
}