Error when trying to use OAuth2 framework in Swift

I am trying to use the OAuth2 framework in Swift to get emails from Gmail's IMAP protocol, but I have run into a bunch of issues. Below is my code.

import Foundation
import OAuth2

// Define the Gmail IMAP server and port
let gmailHost = ""
let gmailPort = 993

// Create an OAuth2 client with your credentials
let oauth2 = OAuth2CodeGrant (
    settings: [
        "client_id": "your_client_id",
        "client_secret": "your_client_secret",
        "authorize_uri": "",
        "token_uri": "",
        "scope": "",

// Request an access token from Google
oauth2.authorize () { authParameters, error in
    if let params = authParameters {
        // Get the access token from the response
        let accessToken = params["access_token"] as! String
        // Generate the authentication string for IMAP
        let authString = "\001auth=Bearer \(accessToken)\001\001"
        // Encode the authentication string in base64
        let authData = (using: .utf8)!
        let authBase64 = authData.base64EncodedString ()
        // Create a socket to connect to the IMAP server
        let socket = try! Socket.create (family: .inet)
        try! socket.connect (to: gmailHost, port: Int32 (gmailPort))
        // Enable SSL/TLS on the socket
        try! socket.setSSL (enabled: true)
        // Read the IMAP server greeting
        let greeting = try! socket.readString ()
        print (greeting)
        // Send the authentication command to the IMAP server
        let authCommand = "A1 AUTHENTICATE XOAUTH2 \(authBase64)\r\n"
        try! socket.write (from: authCommand)
        // Read the IMAP server response
        let response = try! socket.readString ()
        print (response)
        // Check if the authentication was successful
        if response.hasPrefix ("A1 OK") {
            // Authentication succeeded
            print ("IMAP authentication successful")
            // TODO: Add your IMAP commands here
            // Send the logout command to the IMAP server
            let logoutCommand = "A2 LOGOUT\r\n"
            try! socket.write (from: logoutCommand)
            // Read the IMAP server response
            let logoutResponse = try! socket.readString ()
            print (logoutResponse)
        else {
            // Authentication failed
            print ("IMAP authentication failed")
        // Close the socket connection
        socket.close ()
    else {
        // OAuth2 authorization failed
        print ("OAuth2 authorization failed: \(error)")

I get this error when I try to declare the oath2 constant: Cannot find 'OAuth2CodeGrant' in scope. I added OAuth2 to Podfile, installed it, and added OAuth2.framework to Link Binary with Libraries in XCode settings, but I am still running into the same issue. I also get other errors, but this is the main one I'm trying to solve.

Hi Nate, can you add a link to the package you're using? There are a bunch of great OAuth2 libraries for Swift, but it's not clear which one you're trying to use.

Hi @tonyarnold, thanks for the response. Sorry about the confusion -- I've since changed my code to use the "OAuthSwift" library but am struggling to implement it as a Swift beginner. Below is what my code now looks like.

        // create an instance and retain it
        let oauthswift = OAuth2Swift(
            consumerKey:    "**CONSUMERKEY**",
            consumerSecret: "**CONSUMERSECRET**",
            authorizeUrl:   "",
            responseType:   "token"
        let handle = oauthswift.authorize(
            withCallbackURL: "**CALLBACKURL**",
            scope: "**SCOPE**", state:"**STATE**") { result in
            switch result {
            case .success(let (credential, response, parameters)):
              // Do your request
            case .failure(let error):

However, I am unsure of where to get the consumerKey, consumerSecret, callbackURL, scope, and state from -- or what they are, exactly. I assume the consumerKey and consumerSecret are the Client ID and Client Secret from the credentials Google generates for you when you create an OAuth Client ID. What are the callbackURL, scope, and state, though, and where can I get this information from? I'm just struggling with setting these values.

You're correct about the consumerKey and consumerSecret - your OAuth provider will give you these during setup.

The scope is usually an array or comma-delimited list of strings describing the permissions that the token will have (this will depend on the library you're using - some model these as an array of enum cases).

The callback URL is the URL that the web browser will direct the user back to once they've successfully authenticated (and it will append a query of token=… that you can use to extract the token and save it securely). Your app will need to support this custom URL that you provide by Defining a custom URL scheme for your app | Apple Developer Documentation.

Make sense? There's a bunch of libraries out there, some are more manual than others. I've been using @mattie's GitHub - ChimeHQ/OAuthenticator: OAuth 2.0 request authentication and really enjoying how lightweight and integrated it is.

1 Like

That makes sense - thank you!