JSON file resets after I reopen my application - swift

Question

I am storing in a json file some user credentials (email, password, nickname). When I open the app on simulator and create multiple test accounts all works perfectly.
import Foundation
var users: [UserCredentials] = []
func save (email: String, password: String, nickname: String) {
let newUsers = UserCredentials(email: email, password: password, nickname: nickname)
users.append(newUsers)
let encoder = JSONEncoder()
encoder.outputFormatting = .prettyPrinted
do {
let data = try encoder.encode(users)
let url = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!.appendingPathComponent("users.json")
print(url.path)
try data.write(to: url)
} catch {
print("Error encoding JSON: \(error)")
}
}
The issue comes up when I reset the app and I type a new testuser. The json file resets instead of loading the testusers I saved before. Is there a way where the users stay saved in a file even when I restart the simulator?
Before reset:
```JSON
[
{
"email" : "beforereset#yahoo.com",
"nickname" : "beforereset12",
"password" : "test1234A"
},
{
"email" : "beforereset1#yahoo.com",
"nickname" : "beforereset123",
"password" : "test1234A"
}
]
```
After reset:
```JSON
[
{
"email" : "afterreset#yahoo.com",
"nickname" : "afterreset12",
"password" : "1234testA"
}
]
```
Where are the beforereset emails?

Answer 1

This line
try data.write(to: url)
...deletes the existing file's contents and replaces them. Thus every time save runs, the previous contents of the file are lost. (Unless of course you read those contents from the file into users before saving. But no code that you have shown us does that, so I have to conclude that you're not doing it at all.)
Where are the beforereset emails?
Gone. You erased them.