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

Sign in with Phone Number via SMS or WhatsApp using Cotter's Flutter SDK

Steps

1. Import Cotter as a dependency

2. Setup Deep Linking

3. Signing up

4. Logging in

5. Verifying a logged-in user

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.

Using Email

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);
}

Using Phone Number

Use the sign up method to:

• Verify the user's phone number

• Then create a new user in Cotter if successful

Option 1: You want to use Cotter's input form inside the in-app browser. This helps with validating the input.

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

Cotter cotter = new Cotter(apiKeyID: API_KEY_ID);
try {
  var user = await cotter.signUpWithPhoneOTP(
    redirectURL: "myexample://auth_callback",
    channels: [PhoneChannel.SMS, PhoneChannel.WHATSAPP], // optional, default is SMS
  );
} catch (e) {
  print(e);
}

Option 2: You want to use your own input form and buttons. You can present 2 buttons to allow sending the OTP via WhatsApp or SMS.

• Using SMS:

Cotter cotter = new Cotter(apiKeyID: API_KEY_ID);
try {
  var user = await cotter.signUpWithPhoneOTPViaSMS(
              redirectURL: "myexample://auth_callback",
              phone: inputController.text,
            );
} catch (e) {
  print(e);
}

• Using WhatsApp:

Cotter cotter = new Cotter(apiKeyID: API_KEY_ID);
try {
  var user = await cotter.signUpWithPhoneOTPViaWhatsApp(
              redirectURL: "myexample://auth_callback",
              phone: inputController.text,
            );
} catch (e) {
  print(e);
}

Step 4: Logging-In

Using Email

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);
}

Using Phone Number

To authenticate by verifying user's phone number:

Option 1: You want to use Cotter's input form inside the in-app browser. This helps with validating the input.

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.signInWithPhoneOTP(
    redirectURL: "myexample://auth_callback",
    channels: [PhoneChannel.SMS, PhoneChannel.WHATSAPP], // optional, default is SMS
  );
} catch (e) {
  print(e);
}

Option 2: You want to use your own input form and buttons. You can present 2 buttons to allow sending the OTP via WhatsApp or SMS.

• Using SMS:

try {
  var user = await cotter.signInWithPhoneOTPViaSMS(
              redirectURL: "myexample://auth_callback",
              phone: inputController.text,
            );
} catch (e) {
  print(e);
}

• Using WhatsApp:

try {
  var user = await cotter.signInWithPhoneOTPViaWhatsApp(
              redirectURL: "myexample://auth_callback",
              phone: inputController.text,
            );
} catch (e) {
  print(e);
}

To send code/link via SMS or WhatsApp, you'll need to add some balance to you project in the Dashboard.

Step 5: Verifying a logged-in user

Using Email

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);
}

Using Phone Number

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

• Using SMS:

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

• Using WhatsApp:

Cotter cotter = new Cotter(apiKeyID: API_KEY_ID);
try {
  var user = await cotter.getUser();
  user = await user.verifyPhoneWithOTPViaWhatsApp(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:

• Only allow your website/app to use your API Key

• Rate Limit the number of authentication requests

• Enable reCAPTCHA to prevent automated abuse