If I get an error code result from a Cocoa function, is there any easy way to figure out what it means (other than by grepping through all the .h files in the framework bundles)?

+10  A: 

You should look at the <Framework/FrameworkErrors.h> header for whatever framework the method you're using that's returning an error comes from.

For example, an NSError in the Cocoa domain that you get from a method in the Foundation framework will have its code property described in the <Foundation/FoundationErrors.h> header. Similarly with AppKit and <AppKit/AppKitErrors.h> and Core Data and <CoreData/CoreDataErrors.h>.

Also, if you print the description of the NSError in the debugger, it should include not only the error domain and code, but also the name of the actual error code constant so you can look it up in the API reference.

Chris Hanson
+1  A: 

Also, Cocoa's NSError is meant to be displayable to the end user. If you just log it, it should be readable.

If you're talking about Carbon's OSStatus and such, MacErrors.h.