iOS端返回应用后如何获取Google Pay交易响应？

Question #

I'm trying to complete a transaction using Google Pay on iOS, and I've got the initiation code working:

let paValue = "Client_upi_key" // payee address upi id
let pnValue = "Merchant Name" // payee name
let trValue = "1234ABCD" // transaction Id
let urlValue = "http://url/of/the/order/in/your/website" // url for reference
let mcValue = "1234" // retailer category code :- user id
let tnValue = "Purchase in Merchant" // transaction Note
let amValue = "1" // amount to pay
let cuValue = "INR" // currency
let str = "gpay://upi/pay?pa=\(paValue)&pn=\(pnValue)&tr=\(trValue)&mc=\(mcValue)&tn=\(tnValue)&am=\(amValue)&cu=\(cuValue)"
guard let urlString = str.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed) else { return }
guard let url = URL(string: urlString) else { return }
UIApplication.shared.open(url)

Now when users come back to my app after the payment, I want to grab response details like transaction ID, user ID, etc. Is there an iOS equivalent to Android's Intent for this?

Answer #

Great question! On iOS, we don’t have a direct 1:1 equivalent to Android’s Intent system for receiving callback data from another app, but we can absolutely capture Google Pay’s transaction response using custom URL scheme callbacks and a bit of app configuration. Here’s how to implement this:

1. Set Up a Custom URL Scheme for Your App #

First, you need to define a unique URL scheme so Google Pay knows where to send the response:

• Open your Xcode project, navigate to Target > Info > URL Types
• Click the + button to add a new entry
• Fill in the Identifier (e.g., com.yourcompany.yourapp) and set URL Schemes to something unique (like yourapp-gpay) – this is your app’s "callback address"

2. Add the Callback URL to Your Google Pay Payment Request #

Modify your payment URL to include a url parameter pointing to your custom scheme. This tells Google Pay to send the transaction result back to your app when done:

// Define your app's callback URL
let callbackUrl = "yourapp-gpay://transaction-response"
// Update the payment string with the callback
let str = "gpay://upi/pay?pa=\(paValue)&pn=\(pnValue)&tr=\(trValue)&mc=\(mcValue)&tn=\(tnValue)&am=\(amValue)&cu=\(cuValue)&url=\(callbackUrl)"
// Don't forget to percent-encode the string as before!
guard let urlString = str.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed) else { return }
guard let url = URL(string: urlString) else { return }
UIApplication.shared.open(url)

3. Handle the Incoming Callback in Your App #

Next, you need to catch the callback URL when Google Pay opens your app. The implementation depends on whether you’re using AppDelegate or SceneDelegate:

For AppDelegate (UIKit without Scenes):

Add this method to your AppDelegate.swift:

func application(_ app: UIApplication, open url: URL, options: [UIApplication.OpenURLOptionsKey : Any] = [:]) -> Bool {
    // Check if this is a Google Pay callback
    if url.scheme == "yourapp-gpay" && url.host == "transaction-response" {
        // Parse the query parameters from the callback URL
        guard let components = URLComponents(url: url, resolvingAgainstBaseURL: false),
              let queryItems = components.queryItems else { return false }
        
        // Extract the data you need (check Google's docs for full parameter list)
        let transactionId = queryItems.first(where: { $0.name == "tr" })?.value
        let paymentStatus = queryItems.first(where: { $0.name == "status" })?.value
        let utr = queryItems.first(where: { $0.name == "utr" })?.value // Unique Transaction Reference
        let responseCode = queryItems.first(where: { $0.name == "resp" })?.value
        
        // Use this data to update your app's state (e.g., mark order as paid, show success message)
        print("Transaction ID: \(transactionId ?? "N/A")")
        print("Payment Status: \(paymentStatus ?? "N/A")")
        
        return true
    }
    return false
}

For SceneDelegate (UIKit with Scenes):

Add this method to your SceneDelegate.swift:

func scene(_ scene: UIScene, openURLContexts URLContexts: Set<UIOpenURLContext>) {
    guard let url = URLContexts.first?.url else { return }
    
    if url.scheme == "yourapp-gpay" && url.host == "transaction-response" {
        guard let components = URLComponents(url: url, resolvingAgainstBaseURL: false),
              let queryItems = components.queryItems else { return }
        
        let transactionId = queryItems.first(where: { $0.name == "tr" })?.value
        let paymentStatus = queryItems.first(where: { $0.name == "status" })?.value
        
        // Process the response here
        print("Got Google Pay response for transaction: \(transactionId ?? "N/A") | Status: \(paymentStatus ?? "N/A")")
    }
}

4. Key Response Parameters to Look For #

Google Pay will return these common parameters in the callback URL:

• tr: Your original transaction ID (use this to match the request)
• status: Payment outcome (e.g., "SUCCESS", "FAILURE", "SUBMITTED")
• utr: Unique Transaction Reference (only for successful payments)
• resp: UPI response code (e.g., "00" for success)

Pro Tips #

• Always validate the response data: Cross-check the transaction ID with your original order, and verify the status to prevent tampering.
• For better security, consider using Universal Links instead of custom URL schemes – they’re more secure and avoid app hijacking risks.
• Refer to Google’s official UPI documentation for the full list of response parameters and edge cases.

内容的提问来源于stack exchange，提问作者Suhail