Firebase iOS Codelab聊天应用教程中的错误

While building the Firebase tutorial app for iOS in Swift, I got stuck at page 8 in the instructions where we set up the app to allow users to Send Image Messages. It is likely either an error with the code shown in the tutorial, or with my frameworks not being connected properly, but I have updated the pod and cleaned and re-built the app, and still am getting this error for both times Constants.MessageFields.imageUrl are listed.While building the Firebase tutorial app for iO