Swift: upload multiple images to Firestore and assign URLs to object - swift

Question

I'm making an app whereby users post 2 images. I'm using Firebase for storage and as my database.
In my method to upload the images what I had wanted to do was to essentially use this method to return the URLs separately as well. I had written the following:
private func uploadImage(image: UIImage) -> URL? {
let randomName = UUID()
let storageRef = storage.reference().child("\(randomName)/png")
guard let uploadData = image.pngData() else { return nil}
var imageUrl: URL?
storageRef.putData(uploadData, metadata: nil) { (metadata, error) in
if error != nil {
print(error?.localizedDescription)
return
}
storageRef.downloadURL { (url, error) in
if error != nil {
print(error?.localizedDescription)
} else {
imageUrl = url
}
}
}
return imageUrl
}
And then I wrote the following 'post' method which is run when the submit button is tapped:
#objc func post() {
if let question = questionText.text,
let hashtagText = hashtagTextField.text,
let userHandle = Auth.auth().currentUser?.email,
let firstImage = left.image,
let secondImage = right.image,
let firstImageURL = uploadImage(image: firstImage)?.absoluteString,
let secondImageURL = uploadImage(image: secondImage)?.absoluteString
{
db.collection("posts").addDocument(data: [
"firstImage" : firstImageURL,
"secondImage" : secondImageURL,
"question" : question,
"hashtagText" : hashtagText,
"userHandle" : userHandle
]) { (error) in
if let e = error {
print("There was an issue saving data to Firestore, \(e)")
} else {
print("Successfully saved data")
self.dismiss(animated: true, completion: nil)
}
}
}
}
However, obviously the first method is not going to work as the closure is run after imageUrl is returned, therefore returning nil.
I've been trying to figure out how to manage this scenario - I had considered using a loop to populate an array of images but this got messy and I'm sure it is not the standard way to handle this. Any help would be greatly appreciated.

Answer 1

The return imageUrl is in the wrong place. It will return before Firebase has had time to store the image and return the url.
Additionally, the name of the file is not going to work. You currently have
storage.reference().child("\(randomName)/png") // xxxxx/png?
when it should be
storage.reference().child("\(randomName).png") // xxxxx.png
You can't 'return' data from a Firebase closure because firebase is asynchronous - a completion handler may possibly be a solution, but we don't know what the total use case is.
Let's assume you want want to store a users vacation picture in storage and then store that url in Firestore
private func uploadImage(image: UIImage) {
guard let uid = Auth.auth().currentUser?.uid else { return } //this users uid
let storageRef = storage.reference().child(uid).child("vacation.png")
//the path will be storage/users uid/vacation.png
guard let uploadData = image.pngData() else { return nil}
storageRef.putData(uploadData, metadata: nil) { (metadata, error) in
if error != nil {
print(error?.localizedDescription)
return
}
storageRef.downloadURL { (url, error) in
if error != nil {
print(error?.localizedDescription)
} else {
if url != nil {
//it's here where we store the imageUrl in Firestore
let dict = ["theUrl": url?.absoluteURL)]
let userRef = self.db.collection("users").document(uid)
//self.db points to *my* Firestore
userRef.collection("my_pics").addDocument(data: dict)
//will store in firstore/users/uid/docId/theUrl: the url
}
}
}
}
}