I download a sample of UICatalog and run it.When I compile it ,it shows the failed message:There is no SDK with the name or path \"iphoneos4.0\".I find the \"Base SDK\" of UICat
Ok, so I struggled through this too. Based on some of the answers above and from the apple development forum, I was able to figure out what worked for me.
In XCODE, if you notice that the pull down at the top left of the window says "BASE SDK MISSING", you are going to get this error "There is no SDK with the name or path “iphoneos4.0”". To fix the problem:
double click on Group & Files in the upper part of the left pane of xcode. This will open a window
go to the Build tab of the new window
click on the row that says "BaseSDK" and select "Latest iOS (currently set to iOS 3.2)
The Configurations pull down near the top should now say "All Configurations". If not, set it.
close the window.
Now if you try to build, you will get a different error, something like: Code Sign error: The identity 'iPhone Developer: x Xxxxx' doesn't match any identity in any profile ...
So, now what you need to do in xcode is to click on the pull down in the upper left corner (the pull down that had the original BASE SDK MISSING indication, but probably has something different now), and make sure that both "Simulator" and "Debug" are checked as options in the pull-down.
now you should be good to go.