How physical it is to change structure in firebase - ios

Question

If I am storing employee data in firebase which has 3 fields and in future if I want add or remove a field then how physical it is in firebase ? and how can I do it?
I want to use Firebase for one of my iOS project(Swift 4) which I am going to start working on soon so I want to clear the above mentioned concern.

Answer 1

While Lance's answer works - here's a simple alternative. Assume you want to remove an age 'field' from Firebase. Given a structrue
employees
employee_0
name: "Steve"
age: "42"
employee_1
name: "Hank"
age: "37"
if you want to remove the age node from all employee nodes, this will do it
let employeesRef = Database.database().reference().child("employees")
employeesRef.observe(.childAdded, with: { snapshot in
let key = snapshot.key
let refToRemove = employeesRef.child(key).child("age")
refToRemove.removeValue()
})
Adding a field (child node) is even simpler as child node values cannot be nil so when you write the data, it's added to the node
employeesRef.child(employee_key).child("favorite_food").setValue("pizza")
will add a favorite food node with a value of pizza to an employee node.
Note that there are no 'fields' in Firebase, only parent and child nodes which are key: value pairs.

Answer 2

Jay’s answer is the better way to accomplish what you are asking but this is an alternative. If your a beginner this might be easier to understand and start with. As you advance use Jay’s code.
Seems like you want to do something like this.
Your database structure in Firebase is:
root
|
#-012345 // eg. employeeId
|-"firstName": "Hello"
|-"lastName": "World"
|-"age": "25"
You want to add or remove a field there are several ways to do it but this way it's easy. All you have to to is keep track of the original values then add those plus the new values to a Dictionary and exclude whatever you don't want to send to Firebase using the .setValue() method :
// class properties
let rootRef: DatabaseReference? = Database.database().reference()
let employedID = "012345"
let firstName = "Hello" // original value you want to keep
let lastName = "World" // original value you want to keep
let age = "25" // original value you want to REMOVE
lat gender = "female" // NEW value you want ADDED
// press the button to send the write the values to Firebase
#IBAction fileprivate func updateEmployeeButton(_ sender: UIButton) {
// add the values to a dictionary
let dict = [String:Any]()
dict.(firstName, forKey: "firstName")
dict.(lastName, forKey: "lastName")
dict.(gender, forKey: "gender")
let employeeIdRef = rootRef?.child(employedID)
employeeIdRef?.setValue(dict) // call Firebase's .setValue method and pass the dict as an argument
}
Your database structure will now look like this:
root
|
#-012345
|-"firstName": "Hello"
|-"lastName": "World"
|-"gender": "female"
Notice the way I’m proposing complete overwrites what was at that node but Jay’s way keeps what was there but still gets you the changes you want to make.