Xcode playground gets stuck on 'Running playground' or 'Launching simulator' and won't run the code, what to do?

Question

Every time I create a new playground in order to test some code, Xcode gets stuck and won't run the code. It simply presents 'Running playground' or 'Launching simulator' statement at the top of the screen with the loading icon promisingly spinning next to it but nothing happens. Sometimes this continues indefinitely and sometimes Xcode halts and prints this to console :

Playground execution failed: error: Couldn't lookup symbols:
__swift_FORCE_LOAD_$_swiftCoreImage 
__swift_FORCE_LOAD_$_swiftFoundation 
_playground_log_hidden 
_playground_logger_initialize 
_playground_log_postprint 

thread #1: tid = 0xc0cd0, 0x000000010ea7c3c0 MyPlayground`executePlayground, queue = 'com.apple.main-thread', stop reason = breakpoint 1.2

frame #0: 0x000000010ea7c3c0 MyPlayground`executePlayground
frame #1: 0x000000010ea7b9c0 MyPlayground`__37-[XCPAppDelegate enqueueRunLoopBlock]_block_invoke + 32 
frame #2: 0x000000010f59625c CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 12
frame #3: 0x000000010f57b304 CoreFoundation`__CFRunLoopDoBlocks + 356
frame #4: 0x000000010f57aa75 CoreFoundation`__CFRunLoopRun + 901
frame #5: 0x000000010f57a494 CoreFoundation`CFRunLoopRunSpecific + 420
frame #6: 0x0000000114985a6f GraphicsServices`GSEventRunModal + 161
frame #7: 0x0000000110124f34 UIKit`UIApplicationMain + 159
frame #8: 0x000000010ea7b6e9 MyPlayground`main + 201
frame #9: 0x0000000112ad268d libdyld.dylib`start + 1
frame #10: 0x0000000112ad268d libdyld.dylib`start + 1

I am running Xcode 8.0 (8A218a) on macOS Sierra 10.12.

Hardware:
MacBook Pro (13" Mid-2012)
2,5 GHz Intel Core i5
4 GB 1600 MHz Ram DDR3

I have looked around but at least neither of these threads have provided an answer:
https://forums.developer.apple.com/thread/5902
https://github.com/jas/playground/issues/9

Things I have already tried with zero success:

• Restarting Xcode
• Reinstalling Xcode (downgraded to 7.3 but since that didn't help I upgraded back to 8.0)
• Restarting the machine
• Creating a new playground

Do you have any ideas on how to solve this problem? I am new to programming and eagerly trying to learn Swift but Xcode is making it practically impossible...

Thank you in advance, cheers.

Answer 1

Ans. Switch to macOS platform

When you create a Playground, by default it select iOS platform and automatically imports UIKit. It's the UIKit which crashes and stuck all the time. If your (practice) code does not use UIKit then you can switch to MacOS platform. As major (not exact though) difference between iOS and macOS is in APPKit and UIKit.

In the upper right corner of your Xcode Playground, click on show/hide Utilities--> file inspector --> Playground Setting--> Platform--> macOS

See screenShot below:

Answer 2

I have tried the following and it worked for me:

1. press on the bottom "stop playground" button
2. remove the first comment line and make import statement the first line. no space above import.
3. press execute button

Answer 3

In my case, Xcode 8.3.2, it works when I try as steps below:

1. File -> Close "Name.playground"
2. File -> Close Playground
3. Quit Xcode
4. Re-open Xcode

Answer 4

Buggy Simulator's main process is still working even after Xcode closing. So here're the steps:

1. Quit Xcode;
2. Kill com.apple.CoreSimulator.CoreSimulatorService process in Activity Monitor;
3. Launch Xcode and run your Playground.

Answer 5

In my experience, you should:

1. Prevent Swift playground refresh, by holding: the ► arrow at the bottom left part of the Playground and selecting "Manually Run"
2. Quit Xcode
3. Restart Xcode

It works very well.

Answer 6

I have cancelled the comment on the first line. It solved for me. Make sure to try it after you have closed and relaunched Xcode and force quit com.apple.coresimulator from Activity Monitor

Answer 7

Adding import PlaygroundSupport solved the problem for me :)

Answer 8

You can switch to manual processing. It worked for me.

Answer 9

Make sure you kill xcode in the activity monitor before eventually killing com.apple.CoreSimulator.CoreSimulatorService process in the activity monitor. I tried killing the process a number of times and I realized if xcode is still running in the background activity then the com.apple.CoreSimulator.CoreSimulatorService process would pop up again even when you just killed it.

Answer 10

I had the same problem, all that I did is to open Assistance editor and everything works fine with me even when I closed the Assistance editor! Don't ask why it was trial and error. Hope this will help you

Answer 11

I'm using Xcode 10.2 and am getting the same issue. So generally just use Online Swift Playground

This serves my purposes! :-)

Answer 12

In my case the problem was user-induced. I had the assistant editor displayed, but the live view wasn't selected. Make sure it looks like this:

And not like this:

Answer 13

After beating my head on this for a few hours, I realized I had accidentally deleted this, VERY MUCH important line that allows to test UIKit elements before committing my playground onto git:

// Present the view controller in the Live View window
PlaygroundPage.current.liveView = MyViewController()

Facepalm. Hopefully this can help someone from pulling their hair out for a few hours.

Answer 14

For me, the issue was the fact that MyPlayground was syncing to iCloud. Xcode saves your files every few seconds, and it leads to "not responding" states.

So there is a simple solution- just go to:

System Preferences - Apple ID - Apps on this Mac using iCloud- iCloud Drive - Options- And then uncheck "Playground"

That little trick helps to solve frozen "Running".

Answer 15

XCode 12.3 and still same issue happens.

Solution for me is Command + Q ( restart the Xcode )

Answer 16

after runnning a while you will see error message then you go to view>debug area > activate console and then play again worked for me

Answer 17

Check for iCloud storage plan!

If you do have one, it constantly syncs the entire computer which includes Desktop and Document folders. Instead try creating a "Local Files" folder in your Home folder(command+shift+h) and keep your Playground projects there, where it doesn't sync to iCloud.

This worked for me.I hope this works for you as well! :)

Answer 18

Also happens, like in my case, when you've defined a function, but have forgotten to call it?

Answer 19

As if this question didn't have enough answers, I will provide my "solution" to the stuck Swift playgrounds problem:

The one solution I've come across which works nicely for me (so I do not have to restart Xcode):

killall launchd_sim

This will cause the spinning "Running Playground..." to go away and you can trigger a new execution. Be aware: the next execution is going to spin up launchd_sim and all those child processes again. It would probably be best to kill only the relevant child process. But I didn't find it so far.

But I do this only when I'm not using the iOS Simulators in parallel, as the launchd_sim process is a child process of Simulator.

Answer 20

I deleted derived data and clean build folder. This works for me. I was facing with Xcode 11.2.1 and Xcode 10.1 on same machine.

Answer 21

To speed up the build in Xcode Playground and prevent the loading icon to keep spinning forever:

1. go to the sidebar on the right, and change iOS to macOS in Playground Settings
2. instead of importing UIKit, import Foundation

(this would work if you're not trying to use specific stuff from tthe UIKit framework)

Answer 22

I was facing the same issue but after googling and experimenting a bit, I found out that one must always import UIKit before importing any other libs.

Answer 23

Firstly, delete the inbuilt comment line.

Then, even if you put a first line comment back in, it still works.

Answer 24

One last tip that works for me: Make sure no iOS simulator is running. They conflict with each other.