Swift (iOS)

Overview

The Moment Swift SDK enables seamless payment integration into any native iOS application. The SDK provides a clean, idiomatic Swift API with full async/await support to handle the entire payment flow through a native bottom sheet experience. Built for iOS with Swift, the SDK supports both UIKit and SwiftUI workflows.

Key Features

async/await API – Modern Swift concurrency with no callback pyramid
Native Experience – Bottom sheet presentation using native iOS sheet APIs
UIKit & SwiftUI – Works seamlessly with both UI frameworks
Type-Safe – Fully typed closures and result types with Swift-first design
Flexible Callbacks – Handle success, failure, cancellation, retry, and expiry events
Secure – Sensitive payment data handled entirely in Moment’s secure WebView
PCI Compliant – No card data touches your application

How It Works

App launches — Moment(clientKey:) creates the SDK instance; moment.checkout(...) creates and returns the checkout instance, registering your fetchClientToken, fetchSessionStatus, and event closures
Customer taps Pay — checkout.launch() is called
SDK calls fetchClientToken — your closure creates a session on your backend (with a success_url deep link) and returns the client_token
Checkout opens in a native bottom sheet
Customer submits payment — Moment takes over and redirects to the authentication page
Customer completes authentication on the external page
Customer is redirected back to your app via redirect link with ?session_id=abc123
SDK detects the redirect link and calls your fetchSessionStatus("abc123") closure automatically
Your closure fetches the status from your backend, which queries Moment API
SDK routes to the right handler — onSuccess, onFailure, onExpired, or onCancel
Webhooks are delivered to your backend regardless of outcome

Installation

Swift Package Manager (Recommended)

In Xcode, go to File → Add Package Dependencies and enter:

https://github.com/momentpay/sdk/swift

Or add to your Package.swift:

dependencies: [
    .package(url: "https://github.com/momentpay/sdk/swift", from: "1.0.0")
]

CocoaPods

Add to your Podfile:

pod 'MomentSDK'

Then run:

pod install

Platform Configuration

Requirements

iOS 15.0+
Swift 5.7+
Xcode 14+

Quick Start

1. Initialize the SDK and configure checkout

Create the SDK instance with Moment(clientKey:) and configure the checkout product by calling moment.checkout(...). Both are set up once when your app launches — in AppDelegate or your SwiftUI App initializer. You provide two async throwing closures — the SDK calls them automatically at the right moments. Backend endpoints:

server.js

// Called by fetchClientToken when checkout.launch() is triggered
app.post('/api/create-payment-session', async (req, res) => {
  const response = await fetch('https://api.momentpay.net/collect/payment_sessions', {
    method: 'POST',
    headers: {
      'Authorization': 'Bearer sk_test_your_secret_key',
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({
      amount: 10000, // Amount in cents (e.g., R100.00)
      currency: 'ZAR',
      type: 'one_time',
      options: {
        checkout_options: {
          presentation_mode: { mode: 'embedded' },
          success_url: 'yourapp://checkout?session_id={SESSION_ID}', // deep link back to app
        },
      },
    }),
  });
  const { client_token } = await response.json();
  res.json({ client_token });
});

// Called by fetchSessionStatus after customer returns via deep link.
app.get('/api/session-status', async (req, res) => {
  const sessionId = req.query.session_id;
  const response = await fetch(
    `https://api.momentpay.net/collect/payment_sessions/${sessionId}`,
    { headers: { 'Authorization': 'Bearer sk_test_your_secret_key' } }
  );
  const session = await response.json();
  res.json({ status: session.status, ...session });
});

server.py

import requests
from flask import Flask, request, jsonify

app = Flask(__name__)
SECRET_KEY = 'sk_test_your_secret_key'

# Called by fetchClientToken when checkout.launch() is triggered
@app.route('/api/create-payment-session', methods=['POST'])
def create_payment_session():
    response = requests.post(
        'https://api.momentpay.net/collect/payment_sessions',
        headers={
            'Authorization': f'Bearer {SECRET_KEY}',
            'Content-Type': 'application/json',
        },
        json={
            'amount': 10000,  # Amount in cents (e.g., R100.00)
            'currency': 'ZAR',
            'type': 'one_time',
            'options': {
                'checkout_options': {
                    'presentation_mode': {'mode': 'embedded'},
                    'success_url': 'yourapp://checkout?session_id={SESSION_ID}',  # deep link back to app
                },
            },
        },
    )
    data = response.json()
    return jsonify({'client_token': data['client_token']})

# Called by fetchSessionStatus after customer returns via deep link.
@app.route('/api/session-status', methods=['GET'])
def get_session_status():
    session_id = request.args.get('session_id')
    response = requests.get(
        f'https://api.momentpay.net/collect/payment_sessions/{session_id}',
        headers={'Authorization': f'Bearer {SECRET_KEY}'},
    )
    session = response.json()
    return jsonify({'status': session['status'], **session})

server.go

package main

import (
    "bytes"
    "encoding/json"
    "fmt"
    "io"
    "net/http"
)

const secretKey = "sk_test_your_secret_key"
const momentAPI = "https://api.momentpay.net"

// Called by fetchClientToken when checkout.launch() is triggered
func createPaymentSession(w http.ResponseWriter, r *http.Request) {
    payload, _ := json.Marshal(map[string]any{
        "amount":   10000, // Amount in cents (e.g., R100.00)
        "currency": "ZAR",
        "type":     "one_time",
        "options": map[string]any{
            "checkout_options": map[string]any{
                "presentation_mode": map[string]string{"mode": "embedded"},
                "success_url":       "yourapp://checkout?session_id={SESSION_ID}", // deep link back to app
            },
        },
    })

    req, _ := http.NewRequest("POST", momentAPI+"/collect/payment_sessions", bytes.NewBuffer(payload))
    req.Header.Set("Authorization", "Bearer "+secretKey)
    req.Header.Set("Content-Type", "application/json")

    resp, _ := http.DefaultClient.Do(req)
    defer resp.Body.Close()

    var result map[string]any
    json.NewDecoder(resp.Body).Decode(&result)

    w.Header().Set("Content-Type", "application/json")
    json.NewEncoder(w).Encode(map[string]any{"client_token": result["client_token"]})
}

// Called by fetchSessionStatus after customer returns via deep link.
func getSessionStatus(w http.ResponseWriter, r *http.Request) {
    sessionID := r.URL.Query().Get("session_id")

    req, _ := http.NewRequest("GET", fmt.Sprintf("%s/collect/payment_sessions/%s", momentAPI, sessionID), nil)
    req.Header.Set("Authorization", "Bearer "+secretKey)

    resp, _ := http.DefaultClient.Do(req)
    defer resp.Body.Close()

    body, _ := io.ReadAll(resp.Body)
    w.Header().Set("Content-Type", "application/json")
    w.Write(body)
}

func main() {
    http.HandleFunc("/api/create-payment-session", createPaymentSession)
    http.HandleFunc("/api/session-status", getSessionStatus)
    http.ListenAndServe(":8080", nil)
}

functions/index.js

const { onCall } = require('firebase-functions/v2/https');
const axios = require('axios');

// Called by fetchClientToken — creates a payment session
exports.createPaymentSession = onCall(async (request) => {
  const { amount, currency } = request.data;
  const { data } = await axios.post(
    'https://api.momentpay.net/collect/payment_sessions',
    {
      amount,
      currency,
      type: 'one_time',
      options: {
        checkout_options: {
          presentation_mode: { mode: 'embedded' },
          success_url: 'yourapp://checkout?session_id={SESSION_ID}', // deep link back to app
        },
      },
    },
    {
      headers: {
        Authorization: `Bearer ${process.env.MOMENT_SECRET_KEY}`,
        'Content-Type': 'application/json',
      },
    }
  );
  return { client_token: data.client_token };
});

// Called by fetchSessionStatus — retrieves session status after deep link redirect
exports.getSessionStatus = onCall(async (request) => {
  const { sessionId } = request.data;
  const { data } = await axios.get(
    `https://api.momentpay.net/collect/payment_sessions/${sessionId}`,
    { headers: { Authorization: `Bearer ${process.env.MOMENT_SECRET_KEY}` } }
  );
  return { status: data.status, ...data };
});

supabase/functions/create-payment-session/index.ts

import { serve } from 'https://deno.land/std/http/server.ts';

// Invoked by fetchClientToken
serve(async () => {
  const response = await fetch('https://api.momentpay.net/collect/payment_sessions', {
    method: 'POST',
    headers: {
      Authorization: `Bearer ${Deno.env.get('MOMENT_SECRET_KEY')}`,
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({
      amount: 10000,
      currency: 'ZAR',
      type: 'one_time',
      options: {
        checkout_options: {
          presentation_mode: { mode: 'embedded' },
          success_url: 'yourapp://checkout?session_id={SESSION_ID}', // deep link back to app
        },
      },
    }),
  });
  const { client_token } = await response.json();
  return new Response(JSON.stringify({ client_token }), {
    headers: { 'Content-Type': 'application/json' },
  });
});

supabase/functions/get-session-status/index.ts

import { serve } from 'https://deno.land/std/http/server.ts';

// Invoked by fetchSessionStatus
serve(async (req) => {
  const { session_id } = await req.json();
  const response = await fetch(
    `https://api.momentpay.net/collect/payment_sessions/${session_id}`,
    { headers: { Authorization: `Bearer ${Deno.env.get('MOMENT_SECRET_KEY')}` } }
  );
  const session = await response.json();
  return new Response(JSON.stringify({ status: session.status, ...session }), {
    headers: { 'Content-Type': 'application/json' },
  });
});

handler.js

// Called by fetchClientToken — POST /api/create-payment-session
exports.createPaymentSession = async (event) => {
  const response = await fetch('https://api.momentpay.net/collect/payment_sessions', {
    method: 'POST',
    headers: {
      Authorization: `Bearer ${process.env.MOMENT_SECRET_KEY}`,
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({
      amount: 10000,
      currency: 'ZAR',
      type: 'one_time',
      options: {
        checkout_options: {
          presentation_mode: { mode: 'embedded' },
          success_url: 'yourapp://checkout?session_id={SESSION_ID}', // deep link back to app
        },
      },
    }),
  });
  const { client_token } = await response.json();
  return {
    statusCode: 200,
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ client_token }),
  };
};

// Called by fetchSessionStatus — GET /api/session-status?session_id=abc123
exports.getSessionStatus = async (event) => {
  const sessionId = event.queryStringParameters?.session_id;
  const response = await fetch(
    `https://api.momentpay.net/collect/payment_sessions/${sessionId}`,
    { headers: { Authorization: `Bearer ${process.env.MOMENT_SECRET_KEY}` } }
  );
  const session = await response.json();
  return {
    statusCode: 200,
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ status: session.status, ...session }),
  };
};

iOS — initialize once on app launch:

AppDelegate.swift

import MomentSDK

let moment = Moment(clientKey: "pk_your_key_here")
var checkout: MomentCheckout!

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    func application(
        _ application: UIApplication,
        didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
    ) -> Bool {

        checkout = moment.checkout(
            // SDK calls this when checkout.launch() is triggered to get a fresh session token
            fetchClientToken: {
                var request = URLRequest(
                    url: URL(string: "https://your-backend.com/api/create-payment-session")!
                )
                request.httpMethod = "POST"
                request.setValue("application/json", forHTTPHeaderField: "Content-Type")
                let (data, _) = try await URLSession.shared.data(for: request)
                let json = try JSONDecoder().decode([String: String].self, from: data)
                return json["client_token"] ?? ""
            },

            // SDK calls this automatically when a deep link with session_id is detected.
            // Happens after a customer returns from a redirect-based payment (3DS, bank redirect, EFT).
            // Must resolve to a MomentSessionStatus with at least a status field.
            fetchSessionStatus: { sessionId in
                let url = URL(
                    string: "https://your-backend.com/api/session-status?session_id=\(sessionId)"
                )!
                let (data, _) = try await URLSession.shared.data(from: url)
                return try JSONDecoder().decode(MomentSessionStatus.self, from: data)
            },

            onSuccess: { result in
                print("Payment successful: \(result)")
                // Navigate to success screen or update UI
            },
            onFailure: { result in
                print("Payment failed: \(result)")
                // Show error message
            },
            onCancel: { result in
                print("Payment cancelled")
                // Allow user to retry
            },
            onAttemptFailed: { result in
                print("Payment attempt failed: \(result)")
                // User can retry within the checkout
            },
            onExpired: { result in
                print("Payment session expired")
                // Request a new session and retry
            }
        )

        return true
    }

    // Forward deep links to the SDK for redirect payment handling
    func application(
        _ app: UIApplication,
        open url: URL,
        options: [UIApplication.OpenURLOptionsKey: Any] = [:]
    ) -> Bool {
        return moment.handleDeepLink(url)
    }
}

AppDelegate.swift

import MomentSDK
import Alamofire

let moment = Moment(clientKey: "pk_your_key_here")
var checkout: MomentCheckout!

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    func application(
        _ application: UIApplication,
        didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
    ) -> Bool {

        checkout = moment.checkout(
            // SDK calls this when checkout.launch() is triggered to get a fresh session token
            fetchClientToken: {
                let response = try await AF
                    .request(
                        "https://your-backend.com/api/create-payment-session",
                        method: .post
                    )
                    .serializingDecodable([String: String].self)
                    .value
                return response["client_token"] ?? ""
            },

            // SDK calls this automatically when a deep link with session_id is detected.
            // Happens after a customer returns from a redirect-based payment (3DS, bank redirect, EFT).
            fetchSessionStatus: { sessionId in
                return try await AF
                    .request(
                        "https://your-backend.com/api/session-status",
                        parameters: ["session_id": sessionId]
                    )
                    .serializingDecodable(MomentSessionStatus.self)
                    .value
            },

            onSuccess: { result in
                print("Payment successful: \(result)")
                // Navigate to success screen or update UI
            },
            onFailure: { result in
                print("Payment failed: \(result)")
                // Show error message
            },
            onCancel: { result in
                print("Payment cancelled")
                // Allow user to retry
            },
            onAttemptFailed: { result in
                print("Payment attempt failed: \(result)")
                // User can retry within the checkout
            },
            onExpired: { result in
                print("Payment session expired")
                // Request a new session and retry
            }
        )

        return true
    }

    func application(
        _ app: UIApplication,
        open url: URL,
        options: [UIApplication.OpenURLOptionsKey: Any] = [:]
    ) -> Bool {
        return moment.handleDeepLink(url)
    }
}

AppDelegate.swift

import MomentSDK
import FirebaseFunctions

let moment = Moment(clientKey: "pk_your_key_here")
var checkout: MomentCheckout!

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    func application(
        _ application: UIApplication,
        didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
    ) -> Bool {

        let functions = Functions.functions()

        checkout = moment.checkout(
            // SDK calls this when checkout.launch() is triggered to get a fresh session token
            fetchClientToken: {
                let result = try await functions
                    .httpsCallable("createPaymentSession")
                    .call(["amount": 10000, "currency": "ZAR"])
                let data = result.data as? [String: Any]
                return data?["client_token"] as? String ?? ""
            },

            // SDK calls this automatically when a deep link with session_id is detected.
            // Happens after a customer returns from a redirect-based payment (3DS, bank redirect, EFT).
            fetchSessionStatus: { sessionId in
                let result = try await functions
                    .httpsCallable("getSessionStatus")
                    .call(["sessionId": sessionId])
                let data = result.data as? [String: Any] ?? [:]
                return try MomentSessionStatus(from: data)
            },

            onSuccess: { result in
                print("Payment successful: \(result)")
                // Navigate to success screen or update UI
            },
            onFailure: { result in
                print("Payment failed: \(result)")
                // Show error message
            },
            onCancel: { result in
                print("Payment cancelled")
                // Allow user to retry
            },
            onAttemptFailed: { result in
                print("Payment attempt failed: \(result)")
                // User can retry within the checkout
            },
            onExpired: { result in
                print("Payment session expired")
                // Request a new session and retry
            }
        )

        return true
    }

    func application(
        _ app: UIApplication,
        open url: URL,
        options: [UIApplication.OpenURLOptionsKey: Any] = [:]
    ) -> Bool {
        return moment.handleDeepLink(url)
    }
}

AppDelegate.swift

import MomentSDK
import Supabase

let moment = Moment(clientKey: "pk_your_key_here")
var checkout: MomentCheckout!

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    let supabase = SupabaseClient(
        supabaseURL: URL(string: "https://your-project.supabase.co")!,
        supabaseKey: "your-anon-key"
    )

    func application(
        _ application: UIApplication,
        didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
    ) -> Bool {

        checkout = moment.checkout(
            // SDK calls this when checkout.launch() is triggered to get a fresh session token.
            // Invokes a Supabase Edge Function named 'create-payment-session'.
            fetchClientToken: { [weak self] in
                guard let self else { throw MomentSDKError.notInitialized }
                let response: [String: String] = try await self.supabase.functions
                    .invoke("create-payment-session")
                return response["client_token"] ?? ""
            },

            // SDK calls this automatically when a deep link with session_id is detected.
            // Happens after a customer returns from a redirect-based payment (3DS, bank redirect, EFT).
            fetchSessionStatus: { [weak self] sessionId in
                guard let self else { throw MomentSDKError.notInitialized }
                return try await self.supabase.functions
                    .invoke(
                        "get-session-status",
                        options: FunctionInvokeOptions(body: ["session_id": sessionId])
                    )
            },

            onSuccess: { result in
                print("Payment successful: \(result)")
                // Navigate to success screen or update UI
            },
            onFailure: { result in
                print("Payment failed: \(result)")
                // Show error message
            },
            onCancel: { result in
                print("Payment cancelled")
                // Allow user to retry
            },
            onAttemptFailed: { result in
                print("Payment attempt failed: \(result)")
                // User can retry within the checkout
            },
            onExpired: { result in
                print("Payment session expired")
                // Request a new session and retry
            }
        )

        return true
    }

    func application(
        _ app: UIApplication,
        open url: URL,
        options: [UIApplication.OpenURLOptionsKey: Any] = [:]
    ) -> Bool {
        return moment.handleDeepLink(url)
    }
}

YourApp.swift

import SwiftUI
import MomentSDK

let moment = Moment(clientKey: "pk_your_key_here")
var checkout: MomentCheckout!

@main
struct YourApp: App {

    init() {
        checkout = moment.checkout(
            // SDK calls this when checkout.launch() is triggered to get a fresh session token
            fetchClientToken: {
                var request = URLRequest(
                    url: URL(string: "https://your-backend.com/api/create-payment-session")!
                )
                request.httpMethod = "POST"
                request.setValue("application/json", forHTTPHeaderField: "Content-Type")
                let (data, _) = try await URLSession.shared.data(for: request)
                let json = try JSONDecoder().decode([String: String].self, from: data)
                return json["client_token"] ?? ""
            },

            // SDK calls this automatically when a deep link with session_id is detected.
            // Happens after a customer returns from a redirect-based payment (3DS, bank redirect, EFT).
            // Must resolve to a MomentSessionStatus with at least a status field.
            fetchSessionStatus: { sessionId in
                let url = URL(
                    string: "https://your-backend.com/api/session-status?session_id=\(sessionId)"
                )!
                let (data, _) = try await URLSession.shared.data(from: url)
                return try JSONDecoder().decode(MomentSessionStatus.self, from: data)
            },

            onSuccess: { result in
                print("Payment successful: \(result)")
                // Navigate to success screen or update UI
            },
            onFailure: { result in
                print("Payment failed: \(result)")
                // Show error message
            },
            onCancel: { result in
                print("Payment cancelled")
                // Allow user to retry
            },
            onAttemptFailed: { result in
                print("Payment attempt failed: \(result)")
                // User can retry within the checkout
            },
            onExpired: { result in
                print("Payment session expired")
                // Request a new session and retry
            }
        )
    }

    var body: some Scene {
        WindowGroup {
            ContentView()
                .onOpenURL { url in
                    moment.handleDeepLink(url)
                }
        }
    }
}

YourApp.swift

import SwiftUI
import MomentSDK
import Alamofire

let moment = Moment(clientKey: "pk_your_key_here")
var checkout: MomentCheckout!

@main
struct YourApp: App {

    init() {
        checkout = moment.checkout(
            // SDK calls this when checkout.launch() is triggered to get a fresh session token
            fetchClientToken: {
                let response = try await AF
                    .request(
                        "https://your-backend.com/api/create-payment-session",
                        method: .post
                    )
                    .serializingDecodable([String: String].self)
                    .value
                return response["client_token"] ?? ""
            },

            // SDK calls this automatically when a deep link with session_id is detected.
            // Happens after a customer returns from a redirect-based payment (3DS, bank redirect, EFT).
            fetchSessionStatus: { sessionId in
                return try await AF
                    .request(
                        "https://your-backend.com/api/session-status",
                        parameters: ["session_id": sessionId]
                    )
                    .serializingDecodable(MomentSessionStatus.self)
                    .value
            },

            onSuccess: { result in
                print("Payment successful: \(result)")
                // Navigate to success screen or update UI
            },
            onFailure: { result in
                print("Payment failed: \(result)")
                // Show error message
            },
            onCancel: { result in
                print("Payment cancelled")
                // Allow user to retry
            },
            onAttemptFailed: { result in
                print("Payment attempt failed: \(result)")
                // User can retry within the checkout
            },
            onExpired: { result in
                print("Payment session expired")
                // Request a new session and retry
            }
        )
    }

    var body: some Scene {
        WindowGroup {
            ContentView()
                .onOpenURL { url in
                    moment.handleDeepLink(url)
                }
        }
    }
}

YourApp.swift

import SwiftUI
import MomentSDK
import FirebaseFunctions

let moment = Moment(clientKey: "pk_your_key_here")
var checkout: MomentCheckout!

@main
struct YourApp: App {

    init() {
        checkout = moment.checkout(
            // SDK calls this when checkout.launch() is triggered to get a fresh session token
            fetchClientToken: {
                let result = try await Functions.functions()
                    .httpsCallable("createPaymentSession")
                    .call(["amount": 10000, "currency": "ZAR"])
                let data = result.data as? [String: Any]
                return data?["client_token"] as? String ?? ""
            },

            // SDK calls this automatically when a deep link with session_id is detected.
            // Happens after a customer returns from a redirect-based payment (3DS, bank redirect, EFT).
            fetchSessionStatus: { sessionId in
                let result = try await Functions.functions()
                    .httpsCallable("getSessionStatus")
                    .call(["sessionId": sessionId])
                let data = result.data as? [String: Any] ?? [:]
                return try MomentSessionStatus(from: data)
            },

            onSuccess: { result in
                print("Payment successful: \(result)")
                // Navigate to success screen or update UI
            },
            onFailure: { result in
                print("Payment failed: \(result)")
                // Show error message
            },
            onCancel: { result in
                print("Payment cancelled")
                // Allow user to retry
            },
            onAttemptFailed: { result in
                print("Payment attempt failed: \(result)")
                // User can retry within the checkout
            },
            onExpired: { result in
                print("Payment session expired")
                // Request a new session and retry
            }
        )
    }

    var body: some Scene {
        WindowGroup {
            ContentView()
                .onOpenURL { url in
                    moment.handleDeepLink(url)
                }
        }
    }
}

YourApp.swift

import SwiftUI
import MomentSDK
import Supabase

let moment = Moment(clientKey: "pk_your_key_here")
var checkout: MomentCheckout!

@main
struct YourApp: App {

    init() {
        let supabase = SupabaseClient(
            supabaseURL: URL(string: "https://your-project.supabase.co")!,
            supabaseKey: "your-anon-key"
        )

        checkout = moment.checkout(
            // SDK calls this when checkout.launch() is triggered to get a fresh session token.
            // Invokes a Supabase Edge Function named 'create-payment-session'.
            fetchClientToken: {
                let response: [String: String] = try await supabase.functions
                    .invoke("create-payment-session")
                return response["client_token"] ?? ""
            },

            // SDK calls this automatically when a deep link with session_id is detected.
            // Happens after a customer returns from a redirect-based payment (3DS, bank redirect, EFT).
            fetchSessionStatus: { sessionId in
                return try await supabase.functions
                    .invoke(
                        "get-session-status",
                        options: FunctionInvokeOptions(body: ["session_id": sessionId])
                    )
            },

            onSuccess: { result in
                print("Payment successful: \(result)")
                // Navigate to success screen or update UI
            },
            onFailure: { result in
                print("Payment failed: \(result)")
                // Show error message
            },
            onCancel: { result in
                print("Payment cancelled")
                // Allow user to retry
            },
            onAttemptFailed: { result in
                print("Payment attempt failed: \(result)")
                // User can retry within the checkout
            },
            onExpired: { result in
                print("Payment session expired")
                // Request a new session and retry
            }
        )
    }

    var body: some Scene {
        WindowGroup {
            ContentView()
                .onOpenURL { url in
                    moment.handleDeepLink(url)
                }
        }
    }
}

2. Launch Checkout

UIKit
SwiftUI

CheckoutViewController.swift

import UIKit
import MomentSDK

class CheckoutViewController: UIViewController {

    @IBAction func payButtonTapped(_ sender: UIButton) {
        // SDK calls fetchClientToken internally — no token management needed here
        checkout.launch(from: self)
    }
}

CheckoutView.swift

import SwiftUI
import MomentSDK

struct CheckoutView: View {
    var body: some View {
        Button("Pay Now") {
            // SDK calls fetchClientToken internally — no token management needed here
            checkout.launch()
        }
        .buttonStyle(.borderedProminent)
    }
}

API Reference

Moment(clientKey:)

Creates the SDK instance. Call once when your app launches — typically stored as a global let before your AppDelegate class or App struct.

Parameter	Type	Required	Description
`clientKey`	`String`	Yes	Your publishable key (`pk_test_...` or `pk_live_...`)

let moment = Moment(clientKey: "pk_test_abc123")

moment.checkout(config)

Creates and returns a MomentCheckout instance for the checkout product. Registers your fetch closures and event handlers — the SDK calls them automatically at the right moments. Typically called in AppDelegate or your SwiftUI App init() and assigned to a global var checkout: MomentCheckout!.

Parameter	Type	Required	Description
`fetchClientToken`	`() async throws -> String`	Yes	Async throwing closure returning a fresh client token. Called by the SDK when `checkout.launch()` is invoked.
`fetchSessionStatus`	`((String) async throws -> MomentSessionStatus)?`	No	Async throwing closure receiving a `sessionId`, returning session status. Called when a deep link with `session_id` is detected after a redirect-based payment. Required only if you use redirect mode.
`onSuccess`	`((MomentResult) -> Void)?`	No	Closure fired when payment succeeds (both embedded and redirect flows)
`onFailure`	`((MomentResult) -> Void)?`	No	Closure fired when payment fails
`onCancel`	`((MomentResult) -> Void)?`	No	Closure fired when user cancels
`onAttemptFailed`	`((MomentResult) -> Void)?`	No	Closure fired when a payment attempt fails (user can retry)
`onExpired`	`((MomentResult) -> Void)?`	No	Closure fired when the payment session expires

Example:

checkout = moment.checkout(
    fetchClientToken: {
        var request = URLRequest(url: URL(string: "https://your-backend.com/api/create-payment-session")!)
        request.httpMethod = "POST"
        let (data, _) = try await URLSession.shared.data(for: request)
        let json = try JSONDecoder().decode([String: String].self, from: data)
        return json["client_token"] ?? ""
    },
    // Only needed if using redirect mode
    fetchSessionStatus: { sessionId in
        let url = URL(string: "https://your-backend.com/api/session-status?session_id=\(sessionId)")!
        let (data, _) = try await URLSession.shared.data(from: url)
        return try JSONDecoder().decode(MomentSessionStatus.self, from: data)
        // MomentSessionStatus must have at minimum: status: "completed" | "failed" | "expired" | "cancelled"
    },
    onSuccess: { result in print("Success:", result) },
    onFailure: { result in print("Failed:", result) },
    onCancel: { result in print("Cancelled") },
    onAttemptFailed: { result in print("Attempt failed:", result) },
    onExpired: { result in print("Expired") }
)

checkout.launch()

Opens the payment checkout in a native bottom sheet. Internally calls your fetchClientToken closure to retrieve a fresh token.

Parameter	Type	Required	Description
`from`	`UIViewController`	UIKit only	The presenting view controller

// UIKit
checkout.launch(from: viewController)

// SwiftUI
checkout.launch()

checkout.close()

Manually dismisses the bottom sheet checkout.

checkout.close()

Security Best Practices

Never embed your secret key (sk_...) in your iOS app — it must only live on your backend
Always create sessions server-side via your backend API
Validate webhooks to confirm payment state before fulfilling orders
Use HTTPS for all backend communication
Handle token expiry — the SDK calls fetchClientToken on every open(), so tokens are always fresh
Use the Keychain to store any persistent credentials — never UserDefaults
Avoid logging sensitive data — do not log client_token or session IDs in production builds

Next Steps

View Sample Applications for end-to-end examples
Create your first Payment Session
Configure Webhooks
Test your integration in Sandbox mode

SDKs

Web

Mobile

Plugins

Overview

Key Features

How It Works

Installation

Swift Package Manager (Recommended)

CocoaPods

Platform Configuration

Requirements

Quick Start

1. Initialize the SDK and configure checkout

2. Launch Checkout

API Reference

Moment(clientKey:)

moment.checkout(config)

checkout.launch()

checkout.close()

Security Best Practices

Next Steps

​Overview

​Key Features

​How It Works

​Installation

​Swift Package Manager (Recommended)

​CocoaPods

​Platform Configuration

​Requirements

​Quick Start

​1. Initialize the SDK and configure checkout

​2. Launch Checkout

​API Reference

​Moment(clientKey:)

​moment.checkout(config)

​checkout.launch()

​checkout.close()

​Security Best Practices

​Next Steps

Overview

Key Features

How It Works

Installation

Swift Package Manager (Recommended)

CocoaPods

Platform Configuration

Requirements

Quick Start

1. Initialize the SDK and configure checkout

2. Launch Checkout

API Reference

Moment(clientKey:)

moment.checkout(config)

checkout.launch()

checkout.close()

Security Best Practices

Next Steps