背景:
替換iOS推送通知的默認左側圖標

實現原理：
1.客戶端實現互動通知擴展，并實現相關代理函數
2.推送消息到蘋果服務器的時候攜帶 "mutable-content": 1 的字段，然后端上的通知擴展程序就會被激活，然后代理函數回調用，下載圖片資源，替換通知圖片

官方例子

{
   "aps" : {
      "category" : "SECRET",
      "mutable-content" : 1,
      "alert" : {
         "title" : "Secret Message!",
         "body"  : "(Encrypted)"
     },
   },
   "ENCRYPTED_DATA" : "Salted__·??Qê$UDì_?ù∞èΩ^?%gq∞N?òQùw"
}

測試例子

{"aps":{"alert":"This is some fancy message.","badge":6,"sound": "default","mutable-content": 1},"avatar_url":"https://img.isupermeet.com/MTcyMjIzNjMxMTczMSM4NzIjanBn.jpg"}

注意："mutable-content": 1 一定到對，否則代理函數無法調用（ps: 筆者做的時候參考了網上資料文檔，有些資料文檔里的 mutable-content 字段是錯誤的，如 mutable_content, 導致無法調試通）

注意：plist文件里的字段順序有嚴格的要求， INStartCallIntent在前，INSendMessageIntent 在后

其他問題：
1.默認創建出來的通知擴展，代碼文件是藍色的

image.png

需要將其轉換成group文件: 選中藍色的文件夾，右鍵選擇 Covert to Group 完成轉換

image.png

2.編譯運行報錯：

ycle inside Runner; building could produce unreliable results.
Cycle details:
→ Target 'Runner' has copy command from '/Users/gg/Library/Developer/Xcode/DerivedData/Runner-bylfgjqadshquibfkfwdljlsxqkj/Build/Products/Release-iphoneos/spns.appex' to '/Users/gg/Library/Developer/Xcode/DerivedData/Runner-bylfgjqadshquibfkfwdljlsxqkj/Build/Products/Release-iphoneos/Runner.app/PlugIns/spns.appex'
○ That command depends on command in Target 'Runner': script phase “[CP] Copy Pods Resources”
○ That command depends on command in Target 'Runner': script phase “[CP] Embed Pods Frameworks”
○ That command depends on command in Target 'Runner': script phase “Thin Binary”
○ Target 'Runner' has process command with output '/Users/gg/Library/Developer/Xcode/DerivedData/Runner-bylfgjqadshquibfkfwdljlsxqkj/Build/Products/Release-iphoneos/Runner.app/Info.plist'
○ Target 'Runner' has copy command from '/Users/gg/Library/Developer/Xcode/DerivedData/Runner-bylfgjqadshquibfkfwdljlsxqkj/Build/Products/Release-iphoneos/spns.appex' to '/Users/gg/Library/Developer/Xcode/DerivedData/Runner-bylfgjqadshquibfkfwdljlsxqkj/Build/Products/Release-iphoneos/Runner.app/PlugIns/spns.appex'

解決參考：stackoverflow
檢查發現我的 Thin Binary 不在最下面，然后移動了最下面解決問題，最終效果如下：

image.png

猜測：Xcode升級后，腳本運行順序出了問題

更多實現細節參考資料：

Zego - 互動通知實現
互動通知實現