Why is XCode freaking out?? I.e., Xcode says methods & properties do not exist but they do!

XCode has been acting really, really strange recently. It is telling me that various classes' methods and properties do not exist - but they do! This is happening both with a custom class, and a Core Data class. I have declared all of the methods and properties, including all the necessary @synthesize calls, and have predeclared the classes using @class in the files which use them and included the .h files, but when I try t开发者_如何学编程o access the methods & properties - it throws errors or warnings, along the lines "No '+newMatrix' method found", "'Collection' may not respond to '+newMatrix'", and "Request for member 'isLanguage' in something not a structure or a union." These have all be declared properly - what could be causing XCode to choke?

Check whether they are in the list of files being compiled. You might not have added the files.

For Core data did you include the Framework?

Make sure you're using the right import statements - these two are very different:

#import <SDKLibrary.h>
#import "CustomClass.h"