Interswitch Payment Gateway SDK for Flutter

The Interswitch Payment Gateway (IPG) SDK for Flutter provides a seamless way to integrate secure payment processing into your mobile applications. Built on top of the robust Interswitch Web Checkout, this SDK simplifies the integration process using a WebView-based redirect flow.

Official Documentation

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Features

• Official Integration: Follows Interswitch Web Redirect standards.
• Cross-Platform: Full support for both iOS and Android.
• Pure Dart: No native dependencies - simple integration without platform-specific setup.
• Multiple Payment Methods: Card, Bank Transfer, USSD, QR Code, OPay, and Wallets.
• Built-in Error Handling: Custom WebpayException for network and WebView errors.

Installation

Add the package to your pubspec.yaml:

dependencies:
  interswitch_payment_gateway: ^0.0.1

OR

Run this command

flutter pub add interswitch_payment_gateway

Then run:

flutter pub get

Note: This package requires webview_flutter which is included as a dependency. No additional setup needed.

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Quick Start

The following example demonstrates a basic payment implementation.

import 'package:flutter/material.dart';
import 'package:interswitch_payment_gateway/interswitch_payment_gateway.dart';

class PaymentScreen extends StatelessWidget {
  // Replace with your actual Interswitch credentials
  // These are test credentials for demonstration
  final webpay = WebpayClient(
    merchantCode: '<merchant-code>',        // Test merchant code
    payItemId: '<pay-item-id>',          // Test pay item ID
    redirectUrl: '<redirect-url>',
    mode: EnvironmentMode.test,
  );

  Future<void> makePayment(BuildContext context) async {

    try {
      final result = await webpay.checkout(
        context: context,
        amount: 100000, // Amount in Kobo (e.g., 100000 = ₦1,000.00)
        txnRef: '<transaction-reference>',
        custEmail: '<customer-email>',
      );

      if (result == null) {
        // User cancelled the payment
        return;
      }

      if (result['resp'] == '00') {
        // Payment successful - verify on your backend
        print('Success! Ref: ${result['txnref']}');
      } else {
        // Payment failed
        print('Failed: ${result['desc']}');
      }
    } on WebpayException catch (e) {
      // Technical error (network, WebView, etc.)
      print('Error: ${e.message}');
    }
  }

  @override
  Widget build(BuildContext context) {
    return ElevatedButton(
      onPressed: () => makePayment(context),
      child: const Text('Pay Now'),
    );
  }
}

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Advanced Usage

With Customer Information

Pre-fill customer details to streamline the checkout experience.

final webpay = WebpayClient(
  merchantCode: 'YOUR_MERCHANT_CODE',
  payItemId: 'YOUR_PAY_ITEM_ID',
  redirectUrl: 'https://your-domain.com/callback',
  mode: EnvironmentMode.live,
  // Default customer info (can be overridden per transaction)
  custName: 'John Doe',
  custEmail: 'john@example.com',
  custId: 'CUST_12345',
  payItemName: 'Premium Subscription',
);

API Reference: WebpayClient Constructor

Parameter	Type	Required	Default	Description
merchantCode	String	Yes	-	Your Interswitch Merchant Code.
payItemId	String	Yes	-	Your Interswitch Pay Item ID.
redirectUrl	String	Yes	-	URL for capturing payment response.
mode	EnvironmentMode	Yes	test	Environment (test or live).
custName	String?	No	-	Default customer name.
custEmail	String?	No	-	Default customer email.
custId	String?	No	-	Default customer ID in your system.
custMobileNo	String?	No	-	Default customer mobile number.
payItemName	String?	No	-	Default name of the item being purchased.

API Reference: checkout() Method

Parameter	Type	Required	Default	Description
context	BuildContext	Yes	-	Flutter build context for navigation.
amount	int	Yes	-	Transaction amount in Kobo (e.g., 100000 = ₦1000).
txnRef	String	Yes	-	Unique transaction reference for the session.
currency	int	No	566	ISO 4217 currency code (Default: 566 for NGN).
custName	String?	No	-	Customer name (overrides default).
custEmail	String?	No	-	Customer email (overrides default).
custId	String?	No	-	Customer ID (overrides default).
custMobileNo	String?	No	-	Customer mobile number (overrides default).
payItemName	String?	No	-	Item name (overrides default).

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Response Handling

Payment Response Fields

Field	Type	Description
resp	String	Response code ("00" = success).
desc	String	Human-readable response description.
txnref	String	Your transaction reference.
amount	String	Transaction amount in Kobo.

Result Scenarios

Scenario	How to Detect	Action
Payment successful	result['resp'] == '00'	Verify on backend, fulfill order.
Payment failed	result['resp'] != '00'	Show result['desc'] to user.
User cancelled	result == null	Return to previous screen.
Technical error	Throws WebpayException	Show error message, allow retry.

Common Response Codes

Code	Description
00	Approved / Successful
Z1	Transaction not found
Z5	Transaction pending
Z6	Transaction processing

For a complete list, see Response Codes.

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Transaction Verification

Important: Always verify transactions on your backend server using Interswitch's Transaction Status API. The client-side response should not be solely relied upon for confirming payment status.

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Test Cards

For testing in sandbox mode, use test cards from Interswitch: Test Cards Documentation

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Example

See the example directory for a complete working implementation.

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Contributing

We welcome contributions! Please submit pull requests or open issues on the GitHub repository.

License

This project is licensed under the MIT License - see the LICENSE file for details.

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Built for the Flutter community