let imageData = UIImageJPEGRepresentation(self.images.firstObject as! UIImage, 0.9)

let myBase64Data = imageData!.base64EncodedString(options: [])

let request = NSMutableURLRequest(url: URL(string: "http://www.example.com/members/mobileapi/uploadSingleFile/")!)
request.httpMethod = "POST"
let postString = "username=tiagotest&password=test&bpo_id=248522&encoded_string=(myBase64Data)&image_name=testFromIphone"

request.httpBody = postString.data(using: String.Encoding.utf8)

let task = URLSession.shared.dataTask(with: request as URLRequest) {

    (data, response, error) in
    guard error == nil && data != nil else {
        print("error=(error)")
        return
    }

    if let httpStatus = response as? HTTPURLResponse , httpStatus.statusCode != 200 {
        print("statusCode should be 200, but is (httpStatus.statusCode)")
        print("response = (response)")
    }

    let responseString = String(data: data!, encoding: String.Encoding.utf8)
    print(responseString!)
}
task.resume()

<key>NSAppTransportSecurity</key>
<dict>
    <key>NSAllowsArbitraryLoads</key>
    <true/>
</dict>