Uploading to Gfycat using AFNetworking in Swift

GfycatHandler

import UIKit

let GfycatPOSTURL = "https://gifaffe.s3.amazonaws.com/"
let GfycatPolicy = "eyAiZXhwaXJhdGlvbiI6ICIyMDIwLTEyLTAxVDEyOjAwOjAwLjAwMFoiLAogICAgICAgICAgICAiY29uZGl0aW9ucyI6IFsKICAgICAgICAgICAgeyJidWNrZXQiOiAiZ2lmYWZmZSJ9LAogICAgICAgICAgICBbInN0YXJ0cy13aXRoIiwgIiRrZXkiLCAiIl0sCiAgICAgICAgICAgIHsiYWNsIjogInByaXZhdGUifSwKCSAgICB7InN1Y2Nlc3NfYWN0aW9uX3N0YXR1cyI6ICIyMDAifSwKICAgICAgICAgICAgWyJzdGFydHMtd2l0aCIsICIkQ29udGVudC1UeXBlIiwgIiJdLAogICAgICAgICAgICBbImNvbnRlbnQtbGVuZ3RoLXJhbmdlIiwgMCwgNTI0Mjg4MDAwXQogICAgICAgICAgICBdCiAgICAgICAgICB9"
let GfycatAWSAccessKeyId = "AKIAIT4VU4B7G2LQYKZQ"
let GfycatSignature = "mk9t/U/wRN4/uU01mXfeTe2Kcoc="

let GfycatTranscodeURL = "http://upload.gfycat.com/transcode/"

class GfycatHandler: NSObject {
    
    func uploadGif(gifData: NSData!, successHandler: ((gfycatURL: NSURL) -> Void)?) {
        var url: NSURL = NSURL(string: GfycatPOSTURL)!
        var request = NSMutableURLRequest(URL: url)
        request.HTTPMethod = "POST"
        request.timeoutInterval = 60
        
        // Create data payload
        var error: NSError?
        var uniqueKey = randomString(10)
        println("Created unique key: \(uniqueKey)")
        var parameters: Dictionary<String, String> = [
            "key" : uniqueKey,
            "acl" : "private",
            "AWSAccessKeyId" : GfycatAWSAccessKeyId,
            "policy" : GfycatPolicy,
            "success_action_status" : "200",
            "signature" : GfycatSignature,
            "Content-Type" : "image/gif"
        ]
        
        var manager = AFHTTPRequestOperationManager()
        manager.POST(GfycatPOSTURL,
            parameters: nil,
            constructingBodyWithBlock: { (formData: AFMultipartFormData!) -> Void in
                for (key, value) in parameters {
                    formData.appendPartWithFormData(value.dataUsingEncoding(NSUTF8StringEncoding)!, name: key)
                }
                // Make sure to add the image last, else AWS throws an error
                formData.appendPartWithFileData(gifData, name: "file", fileName: "photo", mimeType: "image/gif")
            },
            success: { (operation: AFHTTPRequestOperation!, responseObject: AnyObject!) -> Void in
                println("Operation: \(operation)")
                println("Response: \(responseObject)")
                self.transCodeUploadedGif(uniqueKey, successHandler: successHandler)
            }) { (operation: AFHTTPRequestOperation!, error: NSError!) -> Void in
                println("Operation: \(operation)")
                println("Response string: \(operation.responseString)")
                println("Error: \(error)")
        }
    }
    
    func transCodeUploadedGif(uniqueKey: String, successHandler: ((gfycatURL: NSURL) -> Void)? ) {
        var manager = AFHTTPRequestOperationManager()
        var transcodeURL = GfycatTranscodeURL + uniqueKey
        manager.GET(transcodeURL,
            parameters: nil,
            success: { (operation: AFHTTPRequestOperation!, responseObject: AnyObject!) -> Void in
                println("Operation; \(operation)")
                println("Response: \(responseObject)")
                if let json = responseObject as? Dictionary<String, AnyObject> {
                    if let name = json["gfyName"] as? String {
                        if let url = NSURL(string: "http://gfycat.com/"+name) {
                            if successHandler != nil {
                                successHandler!(gfycatURL: url)
                            }
                        }
                    }
                }
            }) { (operation: AFHTTPRequestOperation!, error: NSError!) -> Void in
                println("Operation; \(operation)")
                println("Error: \(error)")
        }
    }
    
    func randomString(length: Int) -> String {
        var string = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
        var characters = Array(string)
        var randomString: String = ""
        var setLength = UInt32(countElements(characters))
        for (var i=0; i < length; i++){
            var rand = arc4random_uniform(setLength)
            var character = characters[Int(rand)]
            randomString.append(character)
        }
        return randomString
    }
}