I upgrade to Yosemite my Mini Mac (yesterday) and after a long hours (almost a day) the installation was succeeded.
I enter in my source code in Xcode 6.0.1 and after automatically install several things (i just saw the message and wait) i can't see the iOS simulators just iOS Device.
I check in Preferences but i have iOS Simulator 7.1 checked but i don't have any other simulator and i can't see 7.1 simulator either.
Thanks for your help.
EDIT **** After install Xcode 6.1 I saw my iOS simulators again in Xcode. I saw a message "installed required components" when first launched the new Xcode version, so I supposed that fix it.
Thanks for your help.
In Xcode 6.1 you can add simulators manually. To do so go to Window -> Devices and press the + symbol left at the bottom.

Then you can choose a combination of device type and iOS version to create.

if the iOS version you wanted is not there you'll be ask to download more simulator and directed to Xcode->Preference->Downloads.

Note: you can directly go to Xcode->Preference->Downloads and download more simulators and it will automatically available in simulator list after download.
来源:https://stackoverflow.com/questions/26440023/where-are-my-ios-simulators-in-xcode-6-after-yosemite-installation