GitHub - Choochmeque/SimpleGoogleSignIn: Lightweight, zero-dependency Google Sign-In for iOS.

A lightweight, dependency-free Google Sign-In implementation for iOS in pure Swift.

Features

✅ Zero external dependencies - Uses only iOS system frameworks
✅ Modern OAuth 2.0 with PKCE - Secure authentication flow
✅ Token management - Access, refresh, and ID token handling
✅ Simple API - Easy to integrate and use
✅ SwiftUI & UIKit - Compatible with both frameworks
✅ Token refresh - Built-in refresh token support

Requirements

iOS 13.0+
Swift 5.7+
Xcode 14.0+

Installation

Swift Package Manager

Add this package to your project:

dependencies: [
    .package(url: "https://github.com/Choochmeque/SimpleGoogleSignIn.git", from: "1.0.0")
]

Or in Xcode:

File → Add Package Dependencies
Enter the repository URL
Select "SimpleGoogleSignIn" library

Manual Installation

Simply copy SimpleGoogleSignIn.swift to your project. No dependencies needed!

Setup

1. Get Google OAuth 2.0 Credentials

Go to Google Cloud Console
Create a new project or select existing
Enable Google Sign-In API
Create OAuth 2.0 credentials (iOS application)
Add your bundle ID
Copy the Client ID

2. Configure URL Scheme

Add to your Info.plist:

<key>CFBundleURLTypes</key>
<array>
    <dict>
        <key>CFBundleURLSchemes</key>
        <array>
            <!-- Reversed client ID format -->
            <!-- If your client ID is: 123456789-abcdef.apps.googleusercontent.com -->
            <!-- Then your URL scheme is: com.googleusercontent.apps.123456789-abcdef -->
            <string>com.googleusercontent.apps.YOUR_CLIENT_ID</string>
        </array>
    </dict>
</array>

3. Handle URL Callbacks

In your AppDelegate or SceneDelegate:

func application(_ app: UIApplication, open url: URL, options: [UIApplication.OpenURLOptionsKey : Any] = [:]) -> Bool {
    return SimpleGoogleSignIn.shared.handleURL(url)
}

Usage

Configuration

import SimpleGoogleSignIn

// Configure on app launch
let configuration = GoogleSignInConfiguration(
    clientID: "YOUR_CLIENT_ID.apps.googleusercontent.com",
    serverClientID: nil, // Optional: for server-side validation
    hostedDomain: nil    // Optional: restrict to specific domain
)
SimpleGoogleSignIn.shared.configure(configuration: configuration)

Sign In

SimpleGoogleSignIn.shared.signIn(
    presentingViewController: viewController,
    hint: nil, // Optional: pre-fill email address
    scopes: ["openid", "profile", "email"] // Required: OAuth scopes
) { result in
    switch result {
    case .success(let signInResult):
        print("Access Token: \(signInResult.accessToken.tokenString)")
        print("ID Token: \(signInResult.openIdToken ?? "")")
        print("Refresh Token: \(signInResult.refreshToken ?? "")")
        print("Granted Scopes: \(signInResult.grantedScopes ?? [])")
    case .failure(let error):
        print("Sign in failed: \(error)")
    }
}

Sign Out

// Sign out and optionally revoke access token
SimpleGoogleSignIn.shared.signOut(accessToken: accessTokenString) { error in
    if let error = error {
        print("Sign out failed: \(error)")
    } else {
        print("Successfully signed out")
    }
}

// Or sign out without revoking token
SimpleGoogleSignIn.shared.signOut(accessToken: nil) { error in
    // Local sign out only
}

Token Refresh

// Refresh tokens using refresh token
SimpleGoogleSignIn.shared.refreshTokens(refreshToken: refreshTokenString) { result in
    switch result {
    case .success(let signInResult):
        print("New Access Token: \(signInResult.accessToken.tokenString)")
        print("Token expires: \(signInResult.accessToken.expirationDate ?? Date())")
        // Note: refreshToken may be the same as the original
    case .failure(let error):
        print("Refresh failed: \(error)")
    }
}

Check Token Expiration

// GoogleToken provides expiration checking
if accessToken.isExpired {
    // Token has expired, refresh it
}

SwiftUI Example

import SwiftUI
import SimpleGoogleSignIn

struct ContentView: View {
    @State private var signInResult: GoogleSignInResult?
    @State private var isSigningIn = false
    
    var body: some View {
        VStack(spacing: 20) {
            if let result = signInResult {
                Text("Signed In Successfully")
                Text("Access Token: ...\(String(result.accessToken.tokenString.suffix(10)))")
                
                Button("Sign Out") {
                    SimpleGoogleSignIn.shared.signOut(accessToken: result.accessToken.tokenString) { _ in
                        signInResult = nil
                    }
                }
            } else {
                Button("Sign in with Google") {
                    signIn()
                }
                .disabled(isSigningIn)
            }
        }
        .padding()
    }
    
    private func signIn() {
        isSigningIn = true
        guard let windowScene = UIApplication.shared.connectedScenes.first as? UIWindowScene,
              let rootViewController = windowScene.windows.first?.rootViewController else {
            return
        }
        
        SimpleGoogleSignIn.shared.signIn(
            presentingViewController: rootViewController,
            hint: nil,
            scopes: ["openid", "profile", "email"]
        ) { result in
            isSigningIn = false
            switch result {
            case .success(let result):
                signInResult = result
            case .failure(let error):
                print("Sign in failed: \(error)")
            }
        }
    }
}

UIKit Example

import UIKit
import SimpleGoogleSignIn

class SignInViewController: UIViewController {
    private var signInResult: GoogleSignInResult?
    
    override func viewDidLoad() {
        super.viewDidLoad()
        configureGoogleSignIn()
    }
    
    private func configureGoogleSignIn() {
        let configuration = GoogleSignInConfiguration(
            clientID: "YOUR_CLIENT_ID.apps.googleusercontent.com"
        )
        SimpleGoogleSignIn.shared.configure(configuration: configuration)
    }
    
    @IBAction func signInTapped() {
        SimpleGoogleSignIn.shared.signIn(
            presentingViewController: self,
            hint: nil,
            scopes: ["openid", "profile", "email"]
        ) { result in
            switch result {
            case .success(let result):
                self.signInResult = result
                self.handleSignInSuccess(result)
            case .failure(let error):
                self.showError(error)
            }
        }
    }
    
    private func handleSignInSuccess(_ result: GoogleSignInResult) {
        print("Access Token: \(result.accessToken.tokenString)")
        // Navigate to main app or update UI
    }
    
    private func showError(_ error: Error) {
        let alert = UIAlertController(
            title: "Sign In Failed",
            message: error.localizedDescription,
            preferredStyle: .alert
        )
        alert.addAction(UIAlertAction(title: "OK", style: .default))
        present(alert, animated: true)
    }
}

Comparison with Official GoogleSignIn

Feature	SimpleGoogleSignIn	Official GoogleSignIn
Dependencies	None	6+ packages
Size	~570 lines	Thousands of lines
Platform	iOS only	iOS, macOS
Setup Complexity	Simple	Complex
App Attest	❌	✅
EMM Support	❌	✅
Server Auth Code	✅	✅
Token Refresh	✅	✅
PKCE Support	✅	✅

Security Features

PKCE (Proof Key for Code Exchange) for OAuth security
State parameter verification to prevent CSRF attacks
Nonce included in authentication for additional security
Token expiration tracking and validation
SSL/TLS for all network requests
ASWebAuthenticationSession for secure system-level authentication

Error Handling

enum GoogleSignInError: LocalizedError {
    case missingConfiguration
    case missingPresentingViewController
    case authenticationFailed(String)
    case invalidResponse
    case userCancelled
    case networkError(Error)
    case missingURLScheme(String)
    
    var errorDescription: String? {
        switch self {
        case .missingConfiguration:
            return "Google Sign-In configuration is missing"
        case .missingPresentingViewController:
            return "No presenting view controller available"
        case .authenticationFailed(let message):
            return "Authentication failed: \(message)"
        case .invalidResponse:
            return "Invalid response from Google"
        case .userCancelled:
            return "User cancelled sign-in"
        case .networkError(let error):
            return "Network error: \(error.localizedDescription)"
        case .missingURLScheme(let scheme):
            return "Required URL scheme '\(scheme)' is not configured in Info.plist"
        }
    }
}

License

MIT License - see LICENSE file for details.

Contributing

Contributions are welcome! Please feel free to submit pull requests.

Support

For issues or questions, please create an issue in the repository.