iOS development Playground file running stuck problem

Problem: When running the Playground file, it gets stuck as shown in the figure below, and it keeps running.

solution:

1. First close Xcode

Close it directly or enter the following statement in the terminal command line to close

killall Xcode

2. End the simulator process

sudo killall -9 com.apple.CoreSimulator.CoreSimulatorService

3. Delete the existing simulator, including all installed applications

rm -rf ~/Library/Developer/CoreSimulator/Devices

Then reopen the Xcode project project. If you encounter some inexplicable problems with the simulator, you can also do this for a while, and it may have some effects.