The runtime for selected device is not installed error

Question

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

Answer 1

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