I am trying to run application using xcode 6 on ios8 simulator but I am getting error "The runtime for selected device is not installed ".
I have set the command line tool in preferences but no luck. Please help.
This just happened to me right after a beta update to Yosemite 10.10 and Xcode 6.6. I still have XCode 5 installed, and I thought it may have been from deleting XCode 6.5, but putting it back in Applications did not help.
First, make sure you have all devices installed in your Simulator. This could fix it right off the bat.
iOS Simulator --> Hardware --> Device --> Manage Devices
I had all the correct devices installed, however, and was still getting the error. This is what finally fixed it:
XCode --> Open Developer Tool --> iOS Simulator
iOS Simulator --> Reset Content and Settings
Restart computer
After installing Xcode, be sure you "select" it in Terminal, before launching / downloading updates.
ex.
sudo xcode-select -switch /Applications/Xcode6-Beta6.app/Contents/Developer/
Also handy to have around... This command shows your currently selected Xcode version.
sudo xcode-select --print-path
It's because you removed Xcode 5 from your computer.
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.
For me restoring xCode 6 beta 5 helped
I renamed xode 5 back to xcode.app and it worked. iOS simulator will not run if we rename the xcode.
来源：https://stackoverflow.com/questions/24423132/the-runtime-for-selected-device-is-not-installed-error