很多文章都在講怎麼關掉 bitcode,

if you are using a third-party framework or library that was updated for iOS 9, and you don’t want to include bitcode, then you should check to see if a version of the framework was provided without bitcode. See Apple’s note on when to include it in your app bundle:

For iOS apps, bitcode is the default, but optional. If you provide bitcode, all apps and frameworks in the app bundle need to include bitcode. For watchOS apps, bitcode is required.

To disable/enable bitcode in your project, follow these steps:

1. In the project build settings, make sure you have enabled All settings to be visible.
2. The Build Options at the “Build Settings” section down. Select Yes or No for the Enable Bitcode option.

Bitcode is an intermediate representation of a compiled program. Apps you upload to iTunes Connect that contain bitcode will be compiled and linked on the App Store. Including bitcode will allow Apple to re-optimize your app binary in the future without the need to submit a new version of your app to the store.

說的是bitcode是被編譯程式的一種中間形式的程式碼。包含bitcode配置的程式將會在App store上被編譯和連結。bitcode允許蘋果在後期重新優化我們程式的二進位制檔案，而不需要我們重新提交一個新的版本到App store上。