Create an animated gif in swift

gif.swift

func createGIF(with images: [UIImage], loopCount: Int = 0, frameDelay: Double, callback: (data: NSData?, error: NSError?) -> ()) {
    let fileProperties = [kCGImagePropertyGIFDictionary as String: [kCGImagePropertyGIFLoopCount as String: loopCount]]
    let frameProperties = [kCGImagePropertyGIFDictionary as String: [kCGImagePropertyGIFDelayTime as String: frameDelay]]
    
    let documentsDirectory = NSTemporaryDirectory()
    let url = NSURL(fileURLWithPath: documentsDirectory)?.URLByAppendingPathComponent("animated.gif")
    
    if let url = url {
        let destination = CGImageDestinationCreateWithURL(url, kUTTypeGIF, UInt(images.count), nil)
        CGImageDestinationSetProperties(destination, fileProperties)
        
        for i in 0..<images.count {
            CGImageDestinationAddImage(destination, images[i].CGImage, frameProperties)
        }
        
        if CGImageDestinationFinalize(destination) {
            callback(data: NSData(contentsOfURL: url), error: nil)
        } else {
            callback(data: nil, error: NSError())
        }
    } else  {
        callback(data: nil, error: NSError())
    }
}

Swift 4.2 (with rx)

private func createPreviewGIF(with images: [UIImage], loopCount: Int = 0, frameDelay: Double) -> Observable<URL?> {
    
    return Observable.create({ subscriber in

        let fileProperties = [kCGImagePropertyGIFDictionary as String: [kCGImagePropertyGIFLoopCount as String: loopCount]] as CFDictionary
        let frameProperties = [kCGImagePropertyGIFDictionary as String: [kCGImagePropertyGIFDelayTime as String: frameDelay]] as CFDictionary
        
        let documentsDirectory = NSTemporaryDirectory()
        let url = NSURL(fileURLWithPath: documentsDirectory).appendingPathComponent("\(Utils.randomString(length: 8)).gif")
        
        if let url = url, let destination = CGImageDestinationCreateWithURL(url as CFURL, kUTTypeGIF, images.count, nil) {
            
            CGImageDestinationSetProperties(destination, fileProperties)
            
            for i in 0..<images.count {
                
                if let cgImage = images[i].cgImage {
                    CGImageDestinationAddImage(destination, cgImage, frameProperties)
                }
                
            }
            
            if CGImageDestinationFinalize(destination) {
                
                subscriber.onNext(url)
                
            } else {
                
                subscriber.onNext(nil)

            }
            
        } else  {
         
            subscriber.onNext(nil)

        }
        
        subscriber.onCompleted()
        
        return Disposables.create()

    })
    
}