Sign in with Email/Phone Number

Our Flutter SDK offers the easiest way to integrate Cotter 's email/phone verification. You can simply call a function and it does most of the heavy lifting and authentication for you.

Concepts: Learn about how Sign in with Email/Phone Number works.

Overview

Verifying email and phone number in your mobile app using our Flutter SDK consists of the following steps:

  1. Call Cotter's Login function

  2. Setup deep linking

  3. Receive user's email or phone number, and whether or not it's verified

What you're building

Steps

Step 1: Import Cotter as a dependency

Add Cotter to your pubspec.yaml , then run flutter pub get.

pubspec.yaml
dependencies:
  cotter:

Check the latest releases in pub.dev. You may need to restart your flutter for it to run pod install (stop flutter run and re run it).

For Android: Update minSdkVersion to 18 following the installation instructions.

Step 2: Setup Deep Linking

The verification will follow OAuth's PKCE flow which will open an in-app browser where your user can enter the OTP sent to their email/phone.

Pick a unique URL scheme for redirecting the user back to your app after the verification in the in-app browser is successful. For this example, we'll use myexample://auth_callback .

Make sure your URL scheme (the front part before ://) doesn't have an underscore or other special characters. To test it out, enter your Redirect URL here: https://jsfiddle.net/omd02jn5/

Setup in iOS

Add the following to your ios/Runner/Info.plist.

ios/Runner/Info.plist
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>

	<!-- ADD THE LINES FROM HERE -->
	<key>CFBundleURLTypes</key>
	<array>
		<dict>
			<key>CFBundleTypeRole</key>
			<string>Editor</string>
			<key>CFBundleURLName</key>
			<string>myexample</string> <!-- 👈 Change this to your own URL Scheme -->
			<key>CFBundleURLSchemes</key>
			<array>
				<string>myexample</string> <!-- 👈 Change this to your own URL Scheme -->
			</array>
		</dict>
	</array>
	<!-- TO HERE -->

	<key>CFBundleDevelopmentRegion</key>
	<string>en</string>

Setup in Android

Add the following to your android/app/src/main/AndroidManifest.xml.

android/app/src/main/AndroidManifest.xml
<manifest ...>
    <application ...> 
    ...

    <!-- Add the lines from here -->
    <activity android:name="com.linusu.flutter_web_auth.CallbackActivity" >
      <intent-filter android:label="flutter_web_auth">
        <action android:name="android.intent.action.VIEW" />
        <category android:name="android.intent.category.DEFAULT" />
        <category android:name="android.intent.category.BROWSABLE" />
        <!-- 👇 This is for myexample://auth_callback -->
        <data android:scheme="myexample" android:host="auth_callback"/>
      </intent-filter>
    </activity>
    <!-- Until here -->

  </application>
</manifest>

You may need to stop flutter-run and re-run it to see the changes.

Step 3: Signing Up

Make sure you have set up the deep-linking above.

Use the sign up method to:

  • Verify the user's email

  • Then create a new user in Cotter if successful

import 'package:cotter/cotter.dart'; // Import Cotter

Cotter cotter = new Cotter(apiKeyID: API_KEY_ID);
try {
  var user = await cotter.signUpWithEmailOTP(
    redirectURL: "myexample://auth_callback",
    email: inputController.text, // Optional, if you leave this blank, user can enter email in the in-app browser
  );
  print(user);
} catch (e) {
  print(e);
}

Step 4: Logging-In

To authenticate an existing user by verifying their email:

This method will create a new user if one doesn't exist.

Cotter cotter = new Cotter(apiKeyID: API_KEY_ID);
try {
  var user = await cotter.signInWithEmailOTP(
        redirectURL: "myexample://auth_callback",
        email: inputController.text, // Optional, if you leave this blank, user can enter email in the in-app browser
      );
} catch(e) {
  print(e);
}

Step 5: Verifying a logged-in user

To verify the email of a user that is currently logged-in:

Cotter cotter = new Cotter(apiKeyID: API_KEY_ID);
try {
  var user = await cotter.getUser();
  user = await user.verifyEmailWithOTP(redirectURL: "myexample://auth_callback");
} catch (e) {
  print(e);
}

Validating Cotter's Access Token

Checkout how to verify the OAuth Tokens from Cotter here:

pageVerifying JWT Tokens

🎉 You're done!

Getting the Logged-in User

Cotter's SDK automatically saves the logged-in user in your device's secure storage. Check out how to get the user information:

pageGetting the Logged-in User

Getting OAuth Tokens

Cotter also automatically generates an access_token, id_token , and refresh_token that is securely stored in the device's secure storage. Check how to get these tokens:

pageGetting OAuth Tokens

Securing your Project

Since you'll be using your API Key from a front-end website or mobile app, your API_KEY_ID is exposed to anyone inspecting your code. Here are some ways to prevent abuse:

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