Check if file is alias Swift

Question

How can I check if a file is an Alias on Mac? Here is my code so far:

public func getFiles(){
    let folderPath = "/Users/timeBro/Desktop/testfolder"
    let fileManager = NSFileManager.defaultManager()
    let enumerator:NSDirectoryEnumerator = fileManager.enumeratorAtPath(folderPath)!
    
    for url in enumerator.allObjects {
        
        let newurl = NSURL(string: url as! String)
        print("\(url as! String)")
        print(url);
        print(newurl?.isFileReferenceURL())
    }
}

How can I check if the file is an alias?

Answer 1

Update: I initially mistakenly assumed that the only option is to use a CoreFoundation (C API) method, but that's not actually true (thanks): the Foundation (ObjC API) class NSURL does provide a way to detect Finder aliases:

// OSX 10.9+
// Indicates if the specified filesystem path is a Finder alias.
// Returns an optional Boolean: if the lookup failed, such when the path doesn't exist,
// nil is returned.
// Example: isFinderAlias("/path/to/an/alias")
func isFinderAlias(path:String) -> Bool? {
    let aliasUrl = NSURL(fileURLWithPath: path)
    var isAlias:AnyObject? = nil
    do {
        try aliasUrl.getResourceValue(&isAlias, forKey: NSURLIsAliasFileKey)
    } catch _ {}
    return isAlias as! Bool?
}

---

[Not recommended, except as an exercise in using UnsafeMutablePointer<Void>]
Here's how to do it with the C-based CoreFoundation API:

• IsAliasFile() was deprecated in OS X 10.4,
• succeeded by FSIsAliasFile(), which was deprecated in 10.8.
• The current method is to use CFURLCopyResourcePropertyForKey(), which isn't fun to deal with in Swift, due to having to use manual memory management with UnsafeMutablePointer<Void>.

I hope I got the memory management right:

import Foundation

// Indicates if the specified filesystem path is a Finder alias.
// Returns an optional Boolean: if the lookup failed, such when the path
// doesn't exist, nil is returned.
// Example: isFinderAlias("/path/to/an/alias")
func isFinderAlias(path:String) -> Bool? {

    var isAlias:Bool? = nil // Initialize result var.

    // Create a CFURL instance for the given filesystem path.
    // This should never fail, because the existence isn't verified at this point.
    // Note: No need to call CFRelease(fUrl) later, because Swift auto-memory-manages CoreFoundation objects.
    let fUrl = CFURLCreateWithFileSystemPath(nil, path, CFURLPathStyle.CFURLPOSIXPathStyle, false)

    // Allocate void pointer - no need for initialization,
    // it will be assigned to by CFURLCopyResourcePropertyForKey() below.
    let ptrPropVal = UnsafeMutablePointer<Void>.alloc(1)

    // Call the CoreFoundation function that copies the desired information as
    // a CFBoolean to newly allocated memory that prt will point to on return.
    if CFURLCopyResourcePropertyForKey(fUrl, kCFURLIsAliasFileKey, ptrPropVal, nil) {

        // Extract the Bool value from the memory allocated.
        isAlias = UnsafePointer<CFBoolean>(ptrPropVal).memory as Bool

        // Since the CF*() call contains the word "Copy", WE are responsible
        // for destroying (freeing) the memory.
        ptrPropVal.destroy()
    }

    // Deallocate the pointer
    ptrPropVal.dealloc(1)

    return isAlias
}