Function does not return array. Download photos from Firebase Storage matching Firebase Database file names [duplicate] - swift

Question

This question already has answers here:
Returning data from async call in Swift function
(13 answers)
Closed 4 years ago.
I have images stored in FireBase Storage, and matching file name data in FireBase Database, and I want to get those photos and display them (note, there is still some code I need to write because I am not getting EVERY photo from storage. Just those that are returned from a query of the database)
Here is the git repo
This code in DBHandler works, as I can see the print of the image file names
func photoListForLocation() -> [String]{
let file_name:String = String()
var photos = [file_name]
ref.observeSingleEvent(of: .value) { (snapshot) in
if let snapshot = snapshot.children.allObjects as? [DataSnapshot]{
for snap in snapshot {
if let data = snap.value as? [String:Any]{
let imageName:String = data["image_name"]! as! String
photos.append(imageName)
print("photos.append - \(imageName)")
}//if let data
}//for
}//snapshot
}//ref.observeSingleEvent
return photos
}//photoListForLocation
BUT the "return photos" never happens.. So the following in my ViewController does nothing..
let dbHandler:DBHandler = DBHandler()
var fileList = [String]()
fileList = dbHandler.photoListForLocation()
fileList.forEach {fileName in
print("\(fileName)")
}
Of course, if there is a better or simpler way of accomplishing my goal, I'm all ears.
for Mr. Tomato... (see comments)
import Foundation
import FirebaseDatabase
import GoogleMaps
class DBHandler {
var ref:DatabaseReference! = Database.database().reference().child("locations")
var imageCount:Int = 0
func addLocation(coordinate:CLLocationCoordinate2D, rating: Double, imageName: String?){
let location = ["latitude": coordinate.latitude,
"longitude": coordinate.longitude,
"rating": rating,
"image_name": imageName!,
"postDate": ServerValue.timestamp()
] as [String : Any]
self.ref.childByAutoId().setValue(location)
}//end setLocation
func getImageListForLocation(lattitude:Double, longitude:Double) -> [String]{
var images = [String]()
self.ref.observeSingleEvent(of: .value) { (snapshot) in
if let snapshot = snapshot.children.allObjects as? [DataSnapshot]{
for snap in snapshot {
if let data = snap.value as? [String:Any]{
let thisLattitude = data["latitude"]
let thisLongitude = data["longitude"]
guard let imageName = data["image_name"] else {return}
if lattitude == thisLattitude as! Double && longitude == thisLongitude as! Double {
images.append(imageName as! String)
}//if
}//if
}//for
}//if
}//ref
self.imageCount = images.count
return images //DOES NOT RETURN IMAGES!! (FILE NAMES)
}//getImageListForLocation
}//DBHandler

Answer 1

In order to get the photos and display them, you need to store the Storage URL of the photo location in your database for later use. Here are a couple of functions I created for a project that does this.
This application has a list of Angels that it saves and retrieves. Angels have names, numbers, emails, and images. I store a local array of these angels in a datasource I've defined in PageDataSource.sharedInstance(). The boolean crudIsAvailable is to make sure there is a connection. On verifying that CRUD operations are available I being scrubbing the list of angelsToSave:
func saveAngels(_ completion: #escaping(_ error: Error?) -> Void) {
if PageDataSource.sharedInstance.crudIsAvailable == true {
let angelsRef = ref.child("angels")
let myAngelsRef = angelsRef.child(id)
for item in PageDataSource.sharedInstance.angelsToSave {
let angel = PageDataSource.sharedInstance.angels[item]
let angelNameRef = myAngelsRef.child(angel.name!)
var angelToSave = getAngel(angel)
var jpegRepresentation : UIImage? = nil
if let photo = angel.photo {
jpegRepresentation = photo
} else {
jpegRepresentation = UIImage(named: "Anonymous-Seal")
}
if let photoData = UIImageJPEGRepresentation(jpegRepresentation!, 1.0) {
storePhoto(photoData, angel.name!, completion: { (url, err) in
if err != nil {
print(err?.localizedDescription)
angelToSave["photo"] = nil
myAngelsRef.updateChildValues(angelToSave, withCompletionBlock: { (error, ref) in
if error != nil {
completion(error!)
} else {
completion(nil)
}
})
} else {
angelToSave["photo"] = url?.absoluteString
angelNameRef.updateChildValues(angelToSave)
completion(nil)
}
})
}
}
} else {
completion(NSError(domain: "Unavailable", code: 0, userInfo: nil))
}
}
The important part of saveAngels() is if let photoData..... storePhoto() and here is the storePhoto() function.
func storePhoto(_ photo: Data, _ name: String, completion: #escaping (_ result: URL?, _ error: NSError?) -> Void) {
let storageRef = Storage.storage().reference().child(name)
storageRef.putData(photo, metadata: nil) { (storageMetaData, err) in
if err != nil {
completion(nil, NSError(domain: (err?.localizedDescription)!, code: 0, userInfo: nil))
} else {
completion(storageMetaData?.downloadURL(), nil)
}
}
}
The function storePhoto() returns the value of the URL through a completion handler and the saveAngels() function takes that information and uses it to store the data to the realtime database for future use.
For a better understanding here is my Angel object:
class Angel: NSObject {
var name: String?
var email: [String]?
var phone: [String]?
var photo: UIImage?
var filepath: String?
}
And here is how I download the photo:
First, I retrieve the list of photo URLs to an array of "angels" in a datasource singleton on VC load then I load the images as they appear in a collectionView like this.
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cellID", for: indexPath) as! AngelCollectionViewCell
cell.imageView?.contentMode = .scaleAspectFill
cell.activityIndicator.hidesWhenStopped = true
cell.activityIndicator.startAnimating()
if let pic = PageDataSource.sharedInstance.angels[indexPath.row].photo {
cell.imageView?.image = pic
cell.activityIndicator.stopAnimating()
cell.setNeedsLayout()
} else if let imgURL = PageDataSource.sharedInstance.angels[indexPath.row].filepath {
Storage.storage().reference(forURL: imgURL).getData(maxSize: INT64_MAX, completion: { (data, error) in
guard error == nil else {
print("error downloading: \(error!)")
return
}
// render
let img = UIImage.init(data: data!)
// store to datasource
PageDataSource.sharedInstance.angels[indexPath.row].photo = img
// display img
if cell == collectionView.cellForItem(at: indexPath) {
DispatchQueue.main.async {
cell.imageView?.image = img
cell.activityIndicator.stopAnimating()
cell.setNeedsLayout()
}
}
})
} else {
// TODO: TODO: Change Image to a proper placeholder
cell.imageView.image = UIImage(contentsOfFile: "Angels#2x.png")
cell.Label.text = PageDataSource.sharedInstance.angels[indexPath.row].name!
cell.activityIndicator.stopAnimating()
}
return cell
}
The important code really starts with Storage.storage I hope this helps!!