title: Implementing Receipt Validation in Swift 3
body: <p>I am developing an iOS app in Swift 3 and trying to implement receipt validation following this tutorial: <a href="http://savvyapps.com/blog/how-setup-test-auto-renewable-subscription-ios-app" rel="noreferrer">http://savvyapps.com/blog/how-setup-test-auto-renewable-subscription-ios-app</a>. However, the tutorial seems to have been written using an earlier version of Swift, so I had to make several changes. Here is my receiptValidation() function:</p>
  
  <pre><code>func receiptValidation() {
      let receiptPath = Bundle.main.appStoreReceiptURL?.path
      if FileManager.default.fileExists(atPath: receiptPath!){
          var receiptData:NSData?
          do{
              receiptData = try NSData(contentsOf: Bundle.main.appStoreReceiptURL!, options: NSData.ReadingOptions.alwaysMapped)
          }
          catch{
              print("ERROR: " + error.localizedDescription)
          }
          let receiptString = receiptData?.base64EncodedString(options: NSData.Base64EncodingOptions(rawValue: 0))
          let postString = "receipt-data=" + receiptString! + "&amp;password=" + SUBSCRIPTION_SECRET
          let storeURL = NSURL(string:"https://sandbox.itunes.apple.com/verifyReceipt")!
          let storeRequest = NSMutableURLRequest(url: storeURL as URL)
          storeRequest.httpMethod = "POST"
          storeRequest.httpBody = postString.data(using: .utf8)
          let session = URLSession(configuration:URLSessionConfiguration.default)
          let task = session.dataTask(with: storeRequest as URLRequest) { data, response, error in
              do{
                  let jsonResponse:NSDictionary = try JSONSerialization.jsonObject(with: data!, options: JSONSerialization.ReadingOptions.mutableContainers) as! NSDictionary
                  let expirationDate:NSDate = self.expirationDateFromResponse(jsonResponse: jsonResponse)!
                  self.updateIAPExpirationDate(date: expirationDate)
              }
              catch{
                  print("ERROR: " + error.localizedDescription)
              }
          }
          task.resume()
      }
  }
  </code></pre>
  
  <p>The problem shows up when I try to call the expirationDateFromResponse() method. It turns out that the jsonResponse that gets passed to this method only contains: <code>status = 21002;</code>. I looked this up and it means "The data in the receipt-data property was malformed or missing." However, the device I'm testing on has an active sandbox subscription for the product, and the subscription seems to work correctly aside from this issue. Is there something else I still need to do to make sure the receiptData value will be read and encoded correctly, or some other issue that might be causing this problem?</p>
  
  <p>EDIT: </p>
  
  <p>I tried an alternate way of setting storeRequest.httpBody:</p>
  
  <pre><code>func receiptValidation() {
      let receiptPath = Bundle.main.appStoreReceiptURL?.path
      if FileManager.default.fileExists(atPath: receiptPath!){
          var receiptData:NSData?
          do{
              receiptData = try NSData(contentsOf: Bundle.main.appStoreReceiptURL!, options: NSData.ReadingOptions.alwaysMapped)
          }
          catch{
              print("ERROR: " + error.localizedDescription)
          }
          let receiptString = receiptData?.base64EncodedString(options: NSData.Base64EncodingOptions(rawValue: 0)) //.URLEncoded
          let dict = ["receipt-data":receiptString, "password":SUBSCRIPTION_SECRET] as [String : Any]
          var jsonData:Data?
          do{
              jsonData = try JSONSerialization.data(withJSONObject: dict, options: .prettyPrinted)
          }
          catch{
              print("ERROR: " + error.localizedDescription)
          }
          let storeURL = NSURL(string:"https://sandbox.itunes.apple.com/verifyReceipt")!
          let storeRequest = NSMutableURLRequest(url: storeURL as URL)
          storeRequest.httpMethod = "POST"
          storeRequest.httpBody = jsonData!
          let session = URLSession(configuration:URLSessionConfiguration.default)
          let task = session.dataTask(with: storeRequest as URLRequest) { data, response, error in
              do{
                  let jsonResponse:NSDictionary = try JSONSerialization.jsonObject(with: data!, options: JSONSerialization.ReadingOptions.mutableContainers) as! NSDictionary
                  let expirationDate:NSDate = self.expirationDateFromResponse(jsonResponse: jsonResponse)!
                  self.updateIAPExpirationDate(date: expirationDate)
              }
              catch{
                  print("ERROR: " + error.localizedDescription)
              }
          }
          task.resume()
      }
  }
  </code></pre>
  
  <p>However, when I run the app with this code, it hangs upon reaching the line <code>jsonData = try JSONSerialization.data(withJSONObject: dict, options: .prettyPrinted)</code>. It doesn't even make it to the catch block, it just stops doing anything. From what I've seen online, other people seem to have trouble using JSONSerialization.data to set the request httpBody in Swift 3. </p>