How do I detect if a Firebase Storage file exists? - ios

Question

I'm writing a Swift extension on FIRStorageReference to detect if a file exists or not. I am calling metadataWithCompletion(). If the completion block's optional NSError is not set, I think it's safe to assume that the file exists.
If the NSError is set, either something went wrong or the file doesn't exist. The storage documentation on handling errors in iOS states that FIRStorageErrorCodeObjectNotFound is the type of error that I should be checking, but is doesn't resolve (possibly Swiftified into a shorter .Name-style constant?) and I'm not sure what I should be checking it against.
I'd like to be calling completion(nil, false) if FIRStorageErrorCodeObjectNotFound is set somewhere.
Here's my code so far.
extension FIRStorageReference {
func exists(completion: (NSError?, Bool?) -> ()) {
metadataWithCompletion() { metadata, error in
if let error = error {
print("Error: \(error.localizedDescription)")
print("Error.code: \(error.code)")
// This is where I'd expect to be checking something.
completion(error, nil)
return
} else {
completion(nil, true)
}
}
}
}
Many thanks in advance.

Answer 1

You can check the error code like so:
// Check error code after completion
storageRef.metadataWithCompletion() { metadata, error in
guard let storageError = error else { return }
guard let errorCode = FIRStorageErrorCode(rawValue: storageError.code) else { return }
switch errorCode {
case .ObjectNotFound:
// File doesn't exist
case .Unauthorized:
// User doesn't have permission to access file
case .Cancelled:
// User canceled the upload
...
case .Unknown:
// Unknown error occurred, inspect the server response
}
}

Answer 2

Thats a simple code that I use to check if user has already got a user photo by hasChild("") method ,and the reference is here:
https://firebase.google.com/docs/reference/ios/firebasedatabase/interface_f_i_r_data_snapshot.html
hope this can help
let userID = FIRAuth.auth()?.currentUser?.uid
self.databaseRef.child("users").child(userID!).observeEventType(.Value, withBlock: { (snapshot) in
// Get user value
dispatch_async(dispatch_get_main_queue()){
let username = snapshot.value!["username"] as! String
self.userNameLabel.text = username
// check if user has photo
if snapshot.hasChild("userPhoto"){
// set image locatin
let filePath = "\(userID!)/\("userPhoto")"
// Assuming a < 10MB file, though you can change that
self.storageRef.child(filePath).dataWithMaxSize(10*1024*1024, completion: { (data, error) in
let userPhoto = UIImage(data: data!)
self.userPhoto.image = userPhoto
})
}

Answer 3

Swift 5
let storageRef = Storage.storage().reference().child("yourPath").child("\(someFile)") // eg. someVideoFile.mp4
print(storageRef.fullPath) // use this to print out the exact path that your checking to make sure there aren't any errors
storageRef.getMetadata() { (metadata: StorageMetadata?, error) in
if let error = error {
guard let errorCode = (error as NSError?)?.code else {
print("problem with error")
return
}
guard let err = StorageErrorCode(rawValue: errorCode) else {
print("problem with error code")
return
}
switch err {
case .objectNotFound:
print("File doesn't exist")
case .unauthorized:
print("User doesn't have permission to access file")
case .cancelled:
print("User cancelled the download")
case .unknown:
print("Unknown error occurred, inspect the server response")
default:
print("Another error occurred. This is a good place to retry the download")
}
return
}
// Metadata contains file metadata such as size, content-type.
guard let metadata = metadata else {
// an error occured while trying to retrieve metadata
print("metadata error")
return
}
if metadata.isFile {
print("file must exist becaus metaData is a file")
} else {
print("file for metadata doesn't exist")
}
let size = metadata.size
if size != 0 {
print("file must exist because this data has a size of: ", size)
} else {
print("if file size is equal to zero there must be a problem"
}
}
A shorter version without the detailed error check:
let storageRef = Storage.storage().reference().child("yourPath").child("\(someFile)")
storageRef.getMetadata() { (metadata: StorageMetadata?, error) in
if let error = error { return }
guard let metadata = metadata else { return }
if metadata.isFile {
print("file must exist because metaData is a file")
} else {
print("file for metadata doesn't exist")
}
let size = metadata.size
if size != 0 {
print("file must exist because this data has a size of: ", size)
} else {
print("if file size is equal to zero there must be a problem"
}
}