Creating a ZIP archive from a Cocoa application

Question

Are there Objective-C classes that are equivalent to the ones contained in the Java package java.util.zip?
Is to execute a CLI command the only alternative?

Answer 1

As of iOS8/OSX10.10 there is a built-in way to create zip archives using NSFileCoordinatorReadingOptions.ForUploading. A simple example of create zip archives without any non-Cocoa dependencies:

public extension NSURL {

    /// Creates a zip archive of the file/folder represented by this URL and returns a references to the zipped file
    ///
    /// - parameter dest: the destination URL; if nil, the destination will be this URL with ".zip" appended
    func zip(dest: NSURL? = nil) throws -> NSURL {
        let destURL = dest ?? self.URLByAppendingPathExtension("zip")

        let fm = NSFileManager.defaultManager()
        var isDir: ObjCBool = false

        let srcDir: NSURL
        let srcDirIsTemporary: Bool
        if let path = self.path where self.fileURL && fm.fileExistsAtPath(path, isDirectory: &isDir) && isDir.boolValue == true {
            // this URL is a directory: just zip it in-place
            srcDir = self
            srcDirIsTemporary = false
        } else {
            // otherwise we need to copy the simple file to a temporary directory in order for
            // NSFileCoordinatorReadingOptions.ForUploading to actually zip it up
            srcDir = NSURL(fileURLWithPath: NSTemporaryDirectory()).URLByAppendingPathComponent(NSUUID().UUIDString)
            try fm.createDirectoryAtURL(srcDir, withIntermediateDirectories: true, attributes: nil)
            let tmpURL = srcDir.URLByAppendingPathComponent(self.lastPathComponent ?? "file")
            try fm.copyItemAtURL(self, toURL: tmpURL)
            srcDirIsTemporary = true
        }

        let coord = NSFileCoordinator()
        var error: NSError?

        // coordinateReadingItemAtURL is invoked synchronously, but the passed in zippedURL is only valid 
        // for the duration of the block, so it needs to be copied out
        coord.coordinateReadingItemAtURL(srcDir, options: NSFileCoordinatorReadingOptions.ForUploading, error: &error) { (zippedURL: NSURL) -> Void in
            do {
                try fm.copyItemAtURL(zippedURL, toURL: destURL)
            } catch let err {
                error = err as NSError
            }
        }

        if srcDirIsTemporary { try fm.removeItemAtURL(srcDir) }
        if let error = error { throw error }
        return destURL
    }
}

public extension NSData {
    /// Creates a zip archive of this data via a temporary file and returns the zipped contents
    func zip() throws -> NSData {
        let tmpURL = NSURL(fileURLWithPath: NSTemporaryDirectory()).URLByAppendingPathComponent(NSUUID().UUIDString)
        try self.writeToURL(tmpURL, options: NSDataWritingOptions.DataWritingAtomic)
        let zipURL = try tmpURL.zip()
        let fm = NSFileManager.defaultManager()
        let zippedData = try NSData(contentsOfURL: zipURL, options: NSDataReadingOptions())
        try fm.removeItemAtURL(tmpURL) // clean up
        try fm.removeItemAtURL(zipURL)
        return zippedData
    }
}

Answer 2

Aside from reading and writing zip archives in your own process, there's no shame in using NSTask to run zip and unzip.

Answer 3

• There is a zip-framework, http://code.google.com/p/zip-framework/, but it seems to be in an early (version 0.1) stage.

• Others answers on cocoadev: http://cocoadev.com/ZipArchiveLibraryForCocoa

• One answer from there: ZipKit, https://github.com/kolpanic/ZipKit