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
Steve nailed it. This is an Xcode bug. I loaded the NavBar sample and Xcode didn't even offer the simulator as an option, and it complained about the missing SDK even though it was set correctly in the project and wasn't set at all on the target.
Do what Steve said: "The only way I could resolve it (in fact, the only way I could get the option of running in the simulator at all) was to change from debug to release and back. The dropdown still shows Base SDK Missing but if you click it, the simulator options are there and it builds."
I got a similar error after upgrading my iPhone to iOS4.2.1(8C148a). The situation is as following.
I was using Xcode 3.2.4, but it does not support iOS4.2.1. So I downloaded Xcode_3.2.5_and_ios-sdk_4.2_final.dmg which is 3.78GB requiring 9.53GB to install. Then I ran my ap with Xcode 3.2.5. That is where I got the above error message.
Now it is ok. I solve this based on Geowar's answer:
Please be noted that if you have done as Geowar said and the message is still there. Try to close Xcode 3.2.5 and restart it. That is how it works for me.
Another thing is that if you have just upgraded to iOS4.2.1 like me. When you try to load the a/p from Xcode 3.2.5 the first time. Xcode 3.2.5 may still give you "No provision iOS device connected". Please try to go to organizer and click on your iPhone under DEVICES on the left bar. Wait for a while to let Xcode in sync with your iPhone with iOS4.2.1. Then it will work. At least it work for me.
Jesse
I just had a situation where I changed the Base SDK to 4.2 on my project after updating to Xcode 3.2.5, but I kept on getting the "There is no SDK..." error. I finally opened the project file (MyProject.xcodeproj/project.pbxproj) in a text editor and looked around. There was no mention of 4.0 anywhere, only 4.2. BUT when I then saved that file, it all started working in Xcode. Perhaps some permission on the file or something else. Have no idea really, but it worked.