Firebase: delete item from row (Swift 3) - uitableview

Question

I have a tableview showing data from a Firebase console (JASON structure) like this:
chklst-xxx
- avaliation
-students
-KHZAjBi44eZ8JsaswkKI
-teacher: Paul
-datTime: 09.12.2016 12:25pm
-name: Mary Anne
-mark: 7.5
-preceptor: John
-KHWZlh7aasy78ahsiuKIi0
-teacher: Paul
-datTime: 09.12.2016 12:48pm
-name: Anne Caroline
-mark: 9.4
-preceptor: Peter
These data are shown at a tableview, each one, after node students, except the key. I have one function to delete an especific row, as i do with other apps in CoreData (tableview editingStyle):
// FUNC DELETAR
override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
if editingStyle == .delete {
teste.remove(at: indexPath.row)
ref.removeValue() // HERE IS MY DOUBT
tableView.reloadData()
}
}
I can erase the item from the array and from the table, but i just don't know how to do it from Firebase. I have tried other ways with removeValue, but it just didn't work, except an way to erase the whole data, not specifically that row selected.
let ref = FIRDatabase.database().reference().child("avaliation").child("students")
I need some teaching to make this works. Thank you.
Here is my method for Saving this data: (Added 09.12 19:30pm)
func Save(){
let ref = FIRDatabase.database().reference().child("avaliation").child("students").childByAutoId()
referencia.child(“name”).setValue(Name)
referencia.child(“teacher”).setValue(Teacher)
referencia.child("preceptor").setValue(Preceptor)
referencia.child("datTime”).setValue(DateTime)
referencia.child(“mark”).setValue(ResultComFReFC)
}
And here is my Class where I work with the main Array:
import Foundation
import Firebase
struct ChkList {
var name: String?
var teacher: String?
var preceptor: String?
var DateToday: String?
var mark: String?
var key: String!
init(name: String, teacher: String, preceptor: String, mark: String, DateToday: String, key: String = "") {
self.name = name
self.teacher = teacher
self.preceptor = preceptor
self.mark = mark
self.DateToday = DateToday
self.key = key
}
init(snapshot: FIRDataSnapshot) {
key = snapshot.key
let snapshotValue = snapshot.value as! [String: AnyObject]
name = snapshotValue["name"] as? String
teacher = snapshotValue["teacher"] as? String
preceptor = snapshotValue["preceptor"] as? String
mark = snapshotValue["mark"] as? String
DateToday = snapshotValue["DateToday"] as? String
}
func toAnyObject() -> Any {
return [
"name": name,
"teacher": teacher,
"preceptor": preceptor,
"mark": mark,
"DateToday": DateToday ]}}
UPDATE: Tableview EdityingStyle
override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
if editingStyle == .delete {
let ref = FIRDatabase.database().reference().child("avaliation").child("students").childByAutoId()
teste.remove(at: indexPath.row) //Array delet item
let userKeyA = ref.key
ref.child(userKeyA).removeValue()
tableView.reloadData()
}
}

Answer 1

My suggestion, store the pushKey of the user by using 'getKey' method when you push the user details.
chklst-xxx
- avaliation
-students
-KHZAjBi44eZ8JsaswkKI
-teacher: Paul
-userKey:KHZAjBi44eZ8JsaswkKI <--------------
-datTime: 09.12.2016 12:25pm
-name: Mary Anne
-mark: 7.5
-preceptor: John
Now you can retrieve the 'key` of the user. Suppose you are listing, users in the list view and would want to delete a row.
let ref = FIRDatabase.database().reference().child("avaliation").child("students").child(students.getUserKey()).removeValue();
Let me know, if it works.
Update: I don't know swift. But i'll give u an abstract idea.
When you create a new student, you refer student node and push() right. Like below,
DatabaseReference studentsRef = FIRDatabase.database().reference().child("avaliation").child("students").push();
And then you put your data like,
studentRef.child("teacher").setValue("Paul");
studentRef.child("userKey").setValue(studentRef.getKey()); <------------

Answer 2

I did it, using suggests above and studying and trying a lot.
The way to the method works is really capture the userkey.
override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
if editingStyle == .delete {
let user: ChkList = teste[indexPath.row]
let uk = user.key
print("Userkey: \(uk)")
ref.child(uk!).removeValue()
}
}
This way you will have removed the data from Firebase and the row form tableview.

Answer 3

This answer moves the Firebase delete behavior behind the scenes so as
to not interfere with the normal tableview loading mechanisms. One
benefit is reducing the number of calls to Firebase and removing
timing issues from the internal tableview animation process.
What worked for me is getting the Firebase stuff out of the way. In my case, I collect all the keys that I want. During the delete, I remove the values from my local object, and when leaving the scene I call my cleanup method from viewDidDisappear() to sync the updated data back to Firebase:
func syncFavorites() {
//ref is the leaf for the favorites
//clear existing
ref?.removeValue()
//temp collection
var faves = [String:Any]()
//dataArrayKeys is my collection of keys on self
dataArrayKeys.keys.forEach { (key) in
faves.updateValue("true", forKey: key)
}
ref?.updateChildValues(faves)
}
I handle my tableview's delete action using the normal method.
override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
if editingStyle == .delete {
// Delete the row from the data source
if let key = dataArr[indexPath.row]["key"] as? String {
dataArrayKeys.removeValue(forKey: keyToDelete)
dataArr.remove(at: indexPath.row)
}
tableView.deleteRows(at: [indexPath], with: .fade)
self.tableView.reloadData()
}
}
I have no doubt there is probably a better way. This was the simplest possible thing that worked for me.