Firebase download progress observer error Swift 3 - ios

Question

Trying to show firebase download progress, getting error
"value of type FIRStorageRef has no member observe".
This is the code I got from firebase documents and trying to use.
storage = FIRStorage.storage()
let storageRef = storage.reference().child("Audio").child(successFileName)
self.titleLabel.text = self.successTitlename
SwiftSpinner.show("Loading...")
storageRef.downloadURL { url, error in
if error != nil {
SwiftSpinner.show("Couldn't load Audio...Tap to dismiss").addTapHandler({
SwiftSpinner.hide()
})
**Getting error here**
storageRef.observe(.progress) { snapshot in
// Download reported progress
let percentComplete = 100.0 * Double(snapshot.progress!.completedUnitCount)
/ Double(snapshot.progress!.totalUnitCount)
}
}
Any help would be appreciated, thanks in advance.

Answer 1

downloadURL() doesn't generate a download task like the other download functions, as per Download files - Monitor download progress, since it only returns the download URL and not the file's data.
You'll need to use one of the following: write(toFile:) or getData(maxSize:) and finally task.observeStatus(.progress). The first downloads it to a local file while the latter does so in memory.
Sample from the docs (full source):
// Create a reference to the file we want to download
let starsRef = storageRef.child("images/stars.jpg")
// Create local filesystem URL
let localURL = URL(string: "path/to/stars.jpg")!
// Start the download (in this case writing to a file)
let downloadTask = storageRef.write(toFile: localURL)
// Download in memory with a maximum allowed size of 10MB
// let downloadTask = storageRef.getData(maxSize: 10 * 1024 * 1024)
downloadTask.observe(.progress) { snapshot in
// Download reported progress
let percentComplete = 100.0 * Double(snapshot.progress!.completedUnitCount)
/ Double(snapshot.progress!.totalUnitCount)
print("Done: \(percentComplete)%")
}
downloadTask.observe(.success) { snapshot in
// Download completed successfully
print("Downloaded successfully")
}