Let your users market your app

import UIKit// + your subscription SDK's import (provides Purchases)enum AppThunderRef {    static let apiBase = URL(string: "API_BASE")!  // dashboard    /// Fresh installs: from your onboarding code field.    static func applyCode(        _ code: String) { Purchases.shared.attribution.setAttributes(["at_ref": code]) }    /// Checks a code before "applied" UI. Public key.    static func validateCode(        _ code: String, done: @escaping (Bool) -> Void) {        var url = URLComponents(url: apiBase.appendingPathComponent("codes/\(code)"), resolvingAgainstBaseURL: false)!        url.queryItems = [URLQueryItem(name: "public_key", value: "PUBLIC_KEY")]        URLSession.shared.dataTask(with: url.url!) { data, _, _ in            let json = data.flatMap { try? JSONSerialization.jsonObject(with: $0) as? [String: Any] }            done(json?["valid"] as? Bool ?? false)        }.resume()    }    /// The user's OWN code, stored by your backend.    static func share(        code: String, from vc: UIViewController) {        let text = "Use my code \(code): https://yourapp.com/?ref=\(code)"        let sheet = UIActivityViewController(activityItems: [text], applicationActivities: nil)        sheet.popoverPresentationController?.sourceView = vc.view  // iPad        vc.present(sheet, animated: true)    }}

import android.content.*      // Context, Intentimport java.net.*             // URL, HttpURLConnectionimport kotlinx.coroutines.*   // Dispatchers, withContextimport org.json.JSONObject// + your subscription SDK's import (provides Purchases)object AppThunderRef {    /** Fresh installs: from your onboarding code field. */    fun applyCode(        code: String) = Purchases.sharedInstance.setAttributes(mapOf("at_ref" to code))    /** Checks a code before "applied" UI. Public key. */    suspend fun validateCode(        code: String): Boolean = withContext(Dispatchers.IO) {        try {            val q = URLEncoder.encode(code, "UTF-8") + "?public_key=PUBLIC_KEY"            val conn = URL("API_BASE/codes/$q").openConnection() as HttpURLConnection            conn.connectTimeout = 5_000; conn.readTimeout = 5_000            JSONObject(conn.inputStream.bufferedReader().use { it.readText() }).optBoolean("valid")        } catch (_: Exception) { false }    }    /** The user's OWN code, stored by your backend. */    fun share(        context: Context, code: String) {        val text = "Use my code $code: https://yourapp.com/?ref=$code"        val send = Intent(Intent.ACTION_SEND).setType("text/plain").putExtra(Intent.EXTRA_TEXT, text)        context.startActivity(Intent.createChooser(send, null).addFlags(Intent.FLAG_ACTIVITY_NEW_TASK))    }}

import { Share } from 'react-native';import Purchases from 'react-native-purchases';const API_BASE = 'API_BASE'; // dashboardconst PUBLIC_KEY = 'PUBLIC_KEY';export const AppThunderRef = {  /** Fresh installs: from your onboarding code field. */  applyCode(code: string) {    return Purchases.setAttributes({ at_ref: code });  },  /** Checks a code before "applied" UI. Public key. */  validateCode(code: string) {    const url = `${API_BASE}/codes/${encodeURIComponent(code)}?public_key=${PUBLIC_KEY}`;    return fetch(url)      .then((res) => res.json())      .then((json: { valid?: boolean }) => json.valid === true)      .catch(() => false);  },  /** The user's OWN code, stored by your backend. */  share(code: string) {    const message = `Use my code ${code}: https://yourapp.com/?ref=${code}`;    // message only: same text on iOS, iPad, Android    return Share.share({ message });  },};

import 'dart:convert';import 'package:flutter/material.dart';import 'package:http/http.dart' as http;import 'package:purchases_flutter/purchases_flutter.dart';import 'package:share_plus/share_plus.dart';class AppThunderRef {  /// Fresh installs: from your onboarding code field.  static Future<void> applyCode(      String code) => Purchases.setAttributes({'at_ref': code});  /// Checks a code before "applied" UI. Public key.  static Future<bool> validateCode(      String code) async {    try {      final uri = Uri.parse('API_BASE/codes/${Uri.encodeComponent(code)}?public_key=PUBLIC_KEY');      final res = await http.get(uri).timeout(const Duration(seconds: 5));      return (jsonDecode(res.body) as Map<String, dynamic>)['valid'] == true;    } catch (_) { return false; }  }  /// The user's OWN code, stored by your backend.  static Future<void> share(      String code, BuildContext context) {    final box = context.findRenderObject() as RenderBox;    return SharePlus.instance.share(ShareParams(        text: 'Use my code $code: https://yourapp.com/?ref=$code',        sharePositionOrigin: box.localToGlobal(Offset.zero) & box.size)); // iPad  }}

// ── browser, after the snippet from your dashboardconst ref = window.AppThunderRef; // shareBtn, onValid: yoursconst code = ref.getCode();       // from ?ref=, 90 days, first touchref.validateCode(code, onValid);  // show "code applied"// …post `code` as referredBy with your signup form.shareBtn.addEventListener('click', async () => {  const { myCode } = await (await fetch('/api/my-code')).json();  const text = `Use my code ${myCode}:`;  ref.share(myCode, { text });    // share sheet or clipboard});// ── your server (Node) · app, db, stripe: yoursconst at = (path, body) => fetch('API_BASE' + path, {  method: 'POST', body: JSON.stringify(body),  headers: { Authorization: `Bearer ${process.env.AT_SECRET_KEY}`, 'Content-Type': 'application/json' },}).then((r) => r.json());app.post('/signup', async (req, res) => {  const user = await db.createUser(req.body);  const { code } = await at('/codes', { external_user_id: user.id }); // once; 402 w/o card  await db.saveReferralCode(user.id, code);  const session = await stripe.checkout.sessions.create({ mode: 'subscription', /* … */    subscription_data: { metadata: { at_ref: req.body.referredBy } } });  res.json({ url: session.url });});app.get('/api/my-code', async (req, res) => (req.user  ? res.json({ myCode: await db.referralCode(req.user.id) }) : res.sendStatus(401)));// No Stripe? /referrals at signup, /events per payment.