NSString to FSRef conversion doesn't work

Question

For my app I need to use the Carbon file manager API to get the size of a folder (NSEnumerator is slow, and using NSTask with a shell command is even worse). I've imported the Carbon framework, and I'm using this method to get the size of a folder:

http://www.cocoabuilder.com/archive/message/cocoa/2005/5/20/136503

It uses an FSRef as an argument, and my path string is currently an NSString. I tried using this to convert the NSString to an FSRef:

FSRef f;
        OSStatus os_status = FSPathMakeRef((const UInt8 *)[filePath fileSystemRepresentation], &f, NULL);

        if (os_status != noErr) {
            NSLog(@"fsref creation failed");
        }

And then I called the folder size method:

[self fastFolderSizeAtFSRef:f];

However when I try to build, I get this error regarding the above line:

error: incompatible type for argument one of 'fastFolderSizeAtFSRef:'

Any help would be appreciated. Thanks

Answer 1

The "fastFolderSizeAtFSRef" method takes an FSRef* (FSRef pointer). You're giving it an FSRef. It's a one character fix, luckily enough. You have:

[self fastFolderSizeAtFSRef:f];

Simply change that to:

[self fastFolderSizeAtFSRef:&f];

And you should be good to go. However, I was implementing this same method yesterday but was having trouble creating the FSRef itself. I eventually went with the following code:

FSRef convertNSStringToFSRef(NSString * theString) {
    FSRef output;
    const char *filePathAsCString = [theString UTF8String];
    CFURLRef url = CFURLCreateWithBytes(kCFAllocatorDefault, 
                                        (const UInt8 *)filePathAsCString, 
                                        strlen(filePathAsCString),
                                        kCFStringEncodingUTF8,
                                        NULL);
    CFURLGetFSRef(url, &output);
    CFRelease(url);
    return output;
}

This has been working flawlessly for me.

EDIT: I just open sourced the code that I'm using this in. It's these files:

This file adds a method to NSFileManager that uses an FSRef to find the complete size of a directory. This file adds a method to NSString that will convert it to an FSRef.
Everything happens on line 46 of this file.