Swift - Firebase Getting a Facebook Friends UID in Firestore - swift

Question

For a little background - I have a 'Follow Facebook Friends' ViewController where users can view their friends who also have downloaded my app to follow on the app.
I have correctly called the FBSDK to get a list of friends that have also downloaded the app, but now I need to get these friends uid's in Firebase so I can follow/unfollow them accordingly.
Currently, when I get a FB users id - I get the numeric string as mentioned in the facebook documentation. However, the users uid in Firebase is different. Is there a way to find which firebase user correlates with a FB id? Or should I try to store a Facebook User by facebook id in firebase?
var facebookContacts = [User]()
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "facebookContactCell", for: indexPath) as! FacebookContactCell
// Configure the cell...
let user = facebookContacts[indexPath.row]
cell.contactNameLabel.text = user.name
cell.userId = user.documentId
// Set follow button state
if followingArray.contains(cell.userId) {
cell.followButton.isSelected = true
} else {
cell.followButton.isSelected = false
}
let userImageRef = storage.child("userImages/"+(user.documentId)+"/profile_pic.jpg")
// Download in memory with a maximum allowed size of 1MB (1 * 1024 * 1024 bytes)
userImageRef.getData(maxSize: 1 * 1024 * 1024) { (data, error) in
if let error = error {
// Uh-oh, an error occurred! Display Default image
print("Error - unable to download image: \(error)")
cell.contactImageView.image = UIImage(named: "userProfileGray")
} else {
// Data for "locationImages/(locationId).jpg" is returned
cell.contactImageView.image = UIImage(data: data!)
}
SVProgressHUD.dismiss()
}
return cell
}
func getFbFriends() {
let params = ["fields": "id, first_name, last_name, name, email, picture"]
let graphRequest = FBSDKGraphRequest(graphPath: "/me/friends", parameters: params)
let connection = FBSDKGraphRequestConnection()
connection.add(graphRequest, completionHandler: { (connection, result, error) in
if error == nil {
let resultdict = result as! NSDictionary
print("Result Dict: \(resultdict)")
let data : NSArray = resultdict.object(forKey: "data") as! NSArray
for i in 0..<data.count {
let valueDict : NSDictionary = data[i] as! NSDictionary
let id = valueDict.object(forKey: "id") as! String
print("the id value is \(id)")
let name = valueDict.object(forKey: "name") as! String
print("the name value is \(name)")
let picDict = valueDict["picture"] as! NSDictionary
let picData = picDict["data"] as! NSDictionary
let picURL = picData.object(forKey: "url") as! String
print("the url value is \(picURL)")
self.facebookContacts.append(User(name: name, documentId: id))
}
DispatchQueue.main.async {
self.tableView.reloadData()
}
let friends = resultdict.object(forKey: "data") as! NSArray
print("Found \(friends.count) friends")
} else {
print("Error Getting Friends \(String(describing: error))");
}
})
connection.start()
}

Answer 1

I do not think that you can get the UID of your user based on their Facebook ID. It seems that you have two possibilities:
Search by email. This should allow you to pinpoint the person you are looking for.
Implement custom Facebook authentication. It requires a little extra work but is not too difficult to do.