#import using angle brackets < > and quote marks " "

I'm wondering what decides whether you're allowed to use <Header.h> or "Header.h" when you're importing files in Objective-C. So far my observation has been that you use the quote marks "" for files in your project that you've got the implementation source to, and angle brackets <> when you're referencing a library or framework.

But how exactly does that work? What would I have to do to get my own classes to use the brackets? Right now Xcode will not allow me to do that for my own headers.

Also, by looking in some frameworks headers, I see that the headers reference each other with <frameworkname/file.h>. How does that work? It looks a lot like packages in Java, but as far as I know, there is no such thing as a package in Objective-C.

Objective-C has this in common with C/C++; the quoted form is for "local" includes of files (you need to specify the relative path from the current file, e.g. #include "headers/my_header.h"), while the angle-bracket form is for "global" includes -- those found somewhere on the include path passed to the compiler (e.g. #include <math.h>).

So to have your own headers use < > not " " you need to pass either the relative or the absolute path for your header directory to the compiler. See "How to add a global include path for Xcode" for info on how to do that in Xcode.

See this MSDN page for more info.

In C, the convention is that header files in <> bracket are searched in 'system' directories and "" in user or local directories.

The definition of system and local is a bit vague, I guess. I believe it looks in system directories in include path or in CPPFLAGS for <header.h>, and local directory or directory specified with -I to compiler are searched for "header.h" files.

I assume it works similarly for Objective-C.

To import your own classes using "< >" you have to put the header files (*.h) in the lib folder of compiler or set a SYSTEM VARIABLES ponting to your lib folder.

Just stumbled upon the same problem, there are 2 types of search paths is Xcode:

User Header Search Paths
Header Search Paths

If you add your own include folders into Header Search Paths, you can use angled brackets without any problem.

Or set Always Search User Path to YES so you can use angle brackets.