I've just updated Xcode 4.5 via the App Store, from my previous version which I got from my Apple Developer Account. Since the update I can't compile any apps into the Simulator. I can compile onto a device, e.g. my iPhone.
The error I recieve is
fatal error: file
'/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/
Developer/SDKs/iPhoneSimulator6.0.sdk/usr/include/Availability.h'
has been modified since the precompiled header was built
1 error generated.
go in ~/Library/Developer/Xcode/DerivedData/{project name + gobly-gook}
and delete folder with your project name.
EDIT After suggestion
NOTE:
By default Library Folder is hidden so we can't see it.
So we have three way to use this hidden ~/Library folder
1.Unhide Library folder by following command to unhide ~/Library folder
chflags nohidden ~/Library
Now you can see Library folder as /Users//Library
2. Open GO menu of finder and press Alt key and Library will be visible as new menu item.
Select that to open Library folder
3. You can access ~/Library folder by Terminal.
There's easiest way: Just "clean" project (Product > Clean)
You can just open the Organizer (top-right corner of XCode), go to the Projects tab, select your project on the left and then delete the Derived Data.
This happened when I updated Xcode from 6.0.1 to 6.1
I cleaned the project and could compile successfully!!