SwiftUI 预览错误：连接到启动的交互式代理

Question

I received the above error when using the SwiftUI previews feature and can't figure out why this happens. The error always looks something like this:

GenericHumanReadableError: unexpected error occurred

messageRepliedWithError("Connecting to launched interactive agent 1894", Optional(Error Domain=com.apple.dt.xcodepreviews.service Code=17 "connectToPreviewHost: Failed to connect to 1894: (null)" UserInfo={NSLocalizedDescription=connectToPreviewHost: Failed to connect to 1894: (null)}))

I managed to figure out a good way to debug this, please see below

Answer 1

If you head into /Users/USERNAME/Library/Logs/DiagnosticReports you will see the latest crash reports. Open the most recent one (should start with your app name), and it should tell you the reason the app crashed. It'll look something like this:

Application Specific Information:
Fatal error: This request requires an authenticated account: file /Users/USERNAME/Work/AppName/Models/CloudKitAlbumManager.swift, line 101

In my case, it was a fatalError i threw in development for debugging. The previews loads your app and thus call your whole stack and will crash if you like me throws fatalErrors for debugging.

I hope this helps