React Native：没有日志出现在 Xcode 和 react-native run-ios 中会抛出奇怪的错误

Question

While running a React Native App on a real iOS device, Xcode doesn't show any logs in the window it's supposed to print all of them. It's just empty.

Additionally, react-native-run-ios does not start and instead throws this error:

error Cannot read property 'udid' of null.

• The app builds fine and runs on the device. Reloading the app via the shake menu doesn't help.
• React Native version is 0.59.9

Answer 1

Disconnecting and reconnecting the device's cable to the computer and building again makes the logs appear.

react-native run-ios now now throws the expected error:

error Could not find iPhone X simulator.

(or whichever simulator is your default).

I originally started XCode while the phone was already connected. So perhaps it's best to connect your phone to the computer when XCode is already open.