Swift File Download Issue - ios

Question

I am trying to download a plist file from a remote location and use it in the iOS app I am creating. The file is going to be used for calendar details within the app's calendar. The goal is obviously that I can update the remote file instead of having to push updates to the app itself every time we need to make changes to calendar details.
I started with the code used in this example: Download File From A Remote URL
Here is my modified version:
// Create destination URL
let documentsUrl:URL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first as URL!
let destinationFileUrl = documentsUrl.appendingPathComponent("2017.plist")
//let destinationFileUrl = URL(string: Bundle.main.path(forResource: String(currentYear), ofType: "plist")!)
//Create URL to the source file you want to download
let fileURL = URL(string: "https://drive.google.com/open?id=0BwHDQFwaL9DuLThNYWwtQ1VXblk")
let sessionConfig = URLSessionConfiguration.default
let session = URLSession(configuration: sessionConfig)
let request = URLRequest(url:fileURL!)
let task = session.downloadTask(with: request) { (tempLocalUrl, response, error) in
if let tempLocalUrl = tempLocalUrl, error == nil {
// Success
if let statusCode = (response as? HTTPURLResponse)?.statusCode {
print("Successfully downloaded. Status code: \(statusCode)")
}
do {
try FileManager.default.removeItem(at: destinationFileUrl)
try FileManager.default.moveItem(at: tempLocalUrl, to: destinationFileUrl)
print("File was replaced")
print(NSArray(contentsOf: tempLocalUrl))
//print(tempLocalUrl)
} catch (let writeError) {
print("Error creating a file \(String(describing: destinationFileUrl)) : \(writeError)")
}
} else {
print("Error took place while downloading a file. Error description: %#", error?.localizedDescription as Any);
}
}
task.resume()
I originally tried to overwrite the file that is bundled with the app to being with, that resulted in errors. So I instead tried to just save it in the app's documents folder and that removed that error. I had to make sure and remove any previous version of the file because it was giving me a file already exists error after the first run.
While it says everything is working (The outputs for both successful download and replaced file happen) when I print the contents of the array from the downloaded URL it just gives me nil.
This is my first attempt to use any kind of external resources in an app. Before I have always kept everything internal, so I am sure there is something glaringly obvious I am missing.
Update 1:
I realized I didn't have the correct URL to use to download a file from a Google drive. That line of code has been changed to:
let fileURL = URL(string: "https://drive.google.com/uc?export=download&id=0BwHDQFwaL9DuLThNYWwtQ1VXblk")
So now I actually am downloading the plist like I originally thought I was. Even removing the deletion issue mentioned in the first comment, I still can't get the downloaded file to actually replace the existing one.
Update 2:
I have reduced the actual file manipulation down to the following:
do {
try FileManager.default.replaceItemAt(destinationFileUrl, withItemAt: tempLocalUrl)
print("File was replaced")
print(NSArray(contentsOf: destinationFileUrl))
} catch (let writeError) {
print("Error creating a file \(String(describing: destinationFileUrl)) : \(writeError)")
}
} else {
print("Error took place while downloading a file. Error description: %#", error?.localizedDescription as Any);
}
After the replacement is performed the output of the file shows the correct new contents that were downloaded from the internet.
Later in the code when I try and access the file it seems to be nil in content again.

Answer 1

Look at your download completion code. You:
Delete the file at the destination URL (in case there was one
leftover)
MOVE the temp file to the destination URL (removing it from the temp
URL)
Try to load the file from the temp URL.
What's wrong with this picture?

Answer 2

You are trying to get the contents of the moved file. You already moved the file to destination url and then you are trying to get the contents of the file from temporary location.
For getting file data, Please try the following :
let fileData = try! String(contentsOf: destinationFileUrl, encoding: String.Encoding.utf8)
print(fileData)