How do I create a Finder alias within an application?

Question

What is the code necessary to create a Finder alias from a Cocoa application? Are there any differences for that code between OS X 10.5, 10.6, and 10.7?

Answer 1

Since OS X 10.6 you can use NSUrl's writeBookmarkData:toURL:options:error: method

From the documentation:

Creates an alias file on disk at a specified location with specified bookmark data.

Sample code:

NSURL *originalUrl = [NSURL fileURLWithPath:@"/this/is/your/path"];
NSURL *aliasUrl = [NSURL fileURLWithPath:@"/your/alias/path"];
NSData *bookmarkData = [originalUrl bookmarkDataWithOptions: NSURLBookmarkCreationSuitableForBookmarkFile includingResourceValuesForKeys:nil relativeToURL:nil error:NULL];

if(bookmarkData != nil) {
    BOOL success = [NSURL writeBookmarkData:bookmarkData toURL:aliasUrl options:NSURLBookmarkCreationSuitableForBookmarkFile error:NULL];
    if(NO == success) {
        //error
    }
}

However, aliases created in that way are not backwards-compatible to earlier OS X versions (pre 10.6)

Answer 2

Take a look at How to Create an Alias Programmatically.

- (void)makeAliasToFolder:(NSString *)destFolder inFolder:(NSString *)parentFolder withName:(NSString *)name
{
    // Create a resource file for the alias.
    FSRef parentRef;
    CFURLGetFSRef((CFURLRef)[NSURL fileURLWithPath:parentFolder], &parentRef);
    HFSUniStr255 aliasName;
    FSGetHFSUniStrFromString((CFStringRef)name, &aliasName);
    FSRef aliasRef;
    FSCreateResFile(&parentRef, aliasName.length, aliasName.unicode, 0, NULL, &aliasRef, NULL);

    // Construct alias data to write to resource fork.
    FSRef targetRef;
    CFURLGetFSRef((CFURLRef)[NSURL fileURLWithPath:destFolder], &targetRef);
    AliasHandle aliasHandle = NULL;
    FSNewAlias(NULL, &targetRef, &aliasHandle);

    // Add the alias data to the resource fork and close it.
    ResFileRefNum fileReference = FSOpenResFile(&aliasRef, fsRdWrPerm);
    UseResFile(fileReference);
    AddResource((Handle)aliasHandle, 'alis', 0, NULL);
    CloseResFile(fileReference);

    // Update finder info.
    FSCatalogInfo catalogInfo;
    FSGetCatalogInfo(&aliasRef, kFSCatInfoFinderInfo, &catalogInfo, NULL, NULL, NULL);
    FileInfo *theFileInfo = (FileInfo*)(&catalogInfo.finderInfo);
    theFileInfo->finderFlags |= kIsAlias; // Set the alias bit.
    theFileInfo->finderFlags &= ~kHasBeenInited; // Clear the inited bit to tell Finder to recheck the file.
    theFileInfo->fileType = kContainerFolderAliasType;
    FSSetCatalogInfo(&aliasRef, kFSCatInfoFinderInfo, &catalogInfo);
}

You can also use applescript

osascript -e 'tell application "Finder" to make alias file to POSIX file "/Applications/myapp.app" at POSIX file "/Applications/"'