最近在幫人「救火」，開發 IAP 功能，朋友公司高層好奇，IAP 付款介面能否用 Touch ID 或 Face ID，在此我研究了些眉角。😌
什麼是 IAP 呢？全名是 In App Purchase，中文叫應用內購買。
其實我在2014年已開發過 IAP，時隔多年來到2021年，後台設定項目的介面也改頭換面，感覺上已經比過去好設定。
這篇要說明的是，過去只能打密碼來驗證身份，現在已可透過「指紋辨識」或「人臉辨識」，快速付款不用回想密碼多少，也因此讓很多人忘記密碼，蘇菲雅就是這樣。🤭
測試 IAP 最讓人害怕的是測試時怎麼付費？但其實可以透過測試帳號，無限次數付費來反覆測試！
我們會在Sandbox環境中測試，只不過系統跳出來的付款介面，怎麼還是那麼老舊？
應該要像首圖那樣，有著詳細的說明，並指示「用側邊按鈕確認」才是！
網路查到有 Apple 官方工程師說明：
I’m pretty certain that Touch ID is not supported in the sandbox test environement. All TestFlight apps are executed in the sandbox environment. If there is a problem with Touch ID in the production environment, that would be an issue to take up with Apple Care or at a Genius Bar.
rich kubota – rkubota@apple.com
developer technical support CoreOS/Hardware/MFI
而就算是上 Testflight 跟上架 App Store 同一個 IAP 版本，Testflight 的版本還是會跳出 Sandbox 介面。
有問題的工程師問：
In TestFlight, FaceID can not be used on the payment confirmation screen of the in-App purchase (Auto-Renewal) application. Is this a TestFlight specification?
同樣是 Apple 核心工程師回答：
All TestFlight apps operate in the sandbox environment. When you use what you think of as your production iTunes User account with a TestFlight app, you are in fact using a sandbox version of the account. The validation of all users in the sandbox environment is handled by a different server than for production operations. The use of FaceID as well as TouchID as an authentication method for iTunes and App Store purchases is an iOS feature for validating the user in the production environment. This is not a StoreKit feature. When a TestFlight user is reviewing your app, they will need to manually enter their account password when prompted to do so.
rich kubota – rkubota@apple.com
developer technical support CoreOS/Hardware/MFI
所以可以請測試員或管理者不用太擔心，等上架之後若沒有出現期望的付款介面，再來商量怎麼做吧～🤠
參考：
逍遙文工作室 
隨意留個言吧：）～