iPhone - Build Error Target is 3.1.2 but can not find NSPredicate

I'm still pretty new at iPhone development and I'm running into this odd build error which I do not understand. I'm trying开发者_开发技巧 to build and run my iPhone application and XCode is telling me that it can not find NSPredicate. To my understanding it was made available in iPhone SDK 3.0 and I'm trying to build for 3.1. I set the target to being "Simulator - 3.1.2 | Debug" in the top left selection box and then hit "Build and Go". I tried setting it in the target app's info as well.

If anyone can direct me to where/what I can change or any documentation, I would appreciate it.

Thanks.

Have you built your project recently with an older version of the SDK. I have run into similar problems and I found that the first thing to do is to clean your target and then build again.

To clean your target open your targets group, right click or control+click on your target and select clean "_target_name_"

Hope this helps.

NSPredicate is part of the Foundation so if you can't find that something is badly scrambled.

(1) Check for circular imports in the headers. These can cause all kinds of weird problems.

(2) Remove all frameworks, clean all, then add the frameworks back in in order. Make sure the target is set for 3.x.

In the past, when I've hit a build problem like this, I found it easier to create a new project and move my custom source to it than to try to figure out what I screwed up on the original. Life's to short to debug a linker.