Using Xcode 6 on 10.9 no iOS 8.0 simulator available

I've also installed on a 10.10 partition and have access to the iOS 8.0 simulators there, but for some reason when following the same setup process on 10.9 no 8.0 simulators are available, I only have the option to use 'iOS Device'.

My command line tools are the latest ones for Mavericks and selected under 'locations'. If I change my deployment target I can launch a 7.1 simulator. The only potential outlier is that I use iRamDisk to manage simulator and derived data file storage. However, I've disabled this, uninstalled and reinstalled Xcode to no avail. Could other Xcode installations be conflicting?

Any help or ideas are much appreciated. Thanks.

The accepted answer did not work for me, restarting OSX fixed the issue

I had the same problem after restoring from Time Machine on a new MacBook Pro and found the solution from Abel Pascual in the Developer Forums:

1. Open Xcode 6 beta
2. Go to the menu Xcode > Open Developer Tool > iOS Simulator
3. Even if an error dialog shows up, you still would have access to the iOS Simulator's menu
4. Select Hardware > Device > Manage Devices
5. Add (if missing) all the devices that you want, or delete and recreate the ones malfunctioning.

(You can check the devices at ~/Library/Developer/CoreSimulator/Devices).

This Worked for me..Try changing Deployment Target

As mentioned in the Xcode 6 release notes, you will not be able to use the iOS Simulator if you rename Xcode.app after launching it. Currently, the workaround is to just rename it back or reboot.

This issue should be mostly resolved with Xcode 7. There are still a few edge cases, but most users should not experience problems like this any more.

There are different solution to this problem :

1. Download simulators for Xcode Xcode -> Preference -> Downloads

   Here, you can download simulators available in 'Components' tab. Also, download the 'Library' available in Documentation tab. This might be useful help.

2. After downloading if iOS 8 simulator doesn't appears then reboot your Mac.

Step 1 and 2 helped me in fixing issue.

This is likely not the answer anyone here is looking for, but in my build settings the "Supported Platform" was set to iphoneos instead of iOS; when I switched it to iOS it decided that it could run on the Simulators.

However, this also created like 200 errors in my project, so I'm not sure if it's the solution.