メソッドの役割がわからない

Swiftのメソッドの役割がわからないです。
今、サーバーに画像をアップロードするメソッド群を作っています。

   func myImageUploadRequest()
    {

        let myUrl = NSURL(string: "http://www.swiftdeveloperblog.com/http-post-example-script/");
        //let myUrl = NSURL(string: "http://www.boredwear.com/utils/postImage.php");

        let request = NSMutableURLRequest(URL:myUrl!);
        request.HTTPMethod = "POST";
        //ユーザーごとに割り振りたい
        let param = [
            "firstName"  : "Sergey",
            "lastName"    : "Kargopolov",
            "userId"    : "9"
        ]

        let boundary = generateBoundaryString()

        request.setValue("multipart/form-data; boundary=\(boundary)", forHTTPHeaderField: "Content-Type")


        let imageData = UIImageJPEGRepresentation(myImageView.image!, 1)

        if(imageData==nil)  { return; }

        request.HTTPBody = createBodyWithParameters(param, filePathKey: "file", imageDataKey: imageData!, boundary: boundary)


        myActivityIndicator.startAnimating();

        let task = NSURLSession.sharedSession().dataTaskWithRequest(request) {
            data, response, error in

            if error != nil {
                print("error=\(error)")
                return
            }

            // You can print out response object
            print("******* response = \(response)")

            // Print out reponse body
            let responseString = NSString(data: data!, encoding: NSUTF8StringEncoding)
            print("****** response data = \(responseString!)")

            do {
                let json = try NSJSONSerialization.JSONObjectWithData(data!, options: []) as? NSDictionary

                print(json)

                dispatch_async(dispatch_get_main_queue(),{
                    self.myActivityIndicator.stopAnimating()
                    self.myImageView.image = nil;
                });

            }catch
            {
                print(error)
            }

        }

        task.resume()
    }


    func createBodyWithParameters(parameters: [String: String]?, filePathKey: String?, imageDataKey: NSData, boundary: String) -> NSData {
        let body = NSMutableData();

        if parameters != nil {
            for (key, value) in parameters! {
                body.appendString("--\(boundary)\r\n")
                body.appendString("Content-Disposition: form-data; name=\"\(key)\"\r\n\r\n")
                body.appendString("\(value)\r\n")
            }
        }

        let filename = "user-profile.jpg"
        let mimetype = "image/jpg"

        body.appendString("--\(boundary)\r\n")
        body.appendString("Content-Disposition: form-data; name=\"\(filePathKey!)\"; filename=\"\(filename)\"\r\n")
        body.appendString("Content-Type: \(mimetype)\r\n\r\n")
        body.appendData(imageDataKey)
        body.appendString("\r\n")

        body.appendString("--\(boundary)--\r\n")

        return body
    }

    func generateBoundaryString() -> String {
        return "Boundary-\(NSUUID().UUIDString)"
    }


}
extension NSMutableData {

    func appendString(string: String) {
        let data = string.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: true)
        appendData(data!)
    }
}

上記のメソッドの

let boundary = generateBoundaryString()

のgenerateBoundaryString() の役割と

 request.HTTPBody = createBodyWithParameters(param, filePathKey: "file", imageDataKey: imageData!, boundary: boundary)

のcreateBodyWithParameters の役割と

let task = NSURLSession.sharedSession().dataTaskWithRequest(request) {
            data, response, error in

            if error != nil {
                print("error=\(error)")
                return
            }

            // You can print out response object
            print("******* response = \(response)")

            // Print out reponse body
            let responseString = NSString(data: data!, encoding: NSUTF8StringEncoding)
            print("****** response data = \(responseString!)")

            do {
                let json = try NSJSONSerialization.JSONObjectWithData(data!, options: []) as? NSDictionary

                print(json)

                dispatch_async(dispatch_get_main_queue(),{
                    self.myActivityIndicator.stopAnimating()
                    self.myImageView.image = nil;
                });

            }catch
            {
                print(error)
            }

        }

        task.resume()
    }

のコードの役割がわかりません。
Swiftはレファレンスがないのでしょうか？
（調べたいにも調べられず）
上記の３つの部分の役割は何なのでしょうか？