How to globally store a User Class instance in Swift - swift

Question

I have been coding in swift for a short time now and wish to create my first, properly complete application. My application starts with a UITabController (after the logging in part which I have implemented) will come with a "profile" page, where the user can update information about themselves (username etc).
I have therefore created a User class which holds this information and will in the future, communicate with a server to update the users information.
I only want one User class object to be instantiated throughout the application (yet still accessible everywhere) as only one user can be logged in on the phone, what is considered the best practice to do so? It may also be worth noting that the log in section will remember a user is logged in so they won't have to re-log in (using user defaults Boolean for isLoggedIn)
I was thinking about making the User class as a singleton, or somehow making the class instance global (although I am pretty sure making it global isn't great).
Or is there a way to make the instance accessible for every view controller placed in a UITabController class if I create the User class in the tab controller class? What do you recommend?
Thanks all!

Answer 1

This is how I use a single object for user data that both is available in any view controller I want but also allows for the saving of data. This utilizes Realm for swift for saving data. To call the data you just create the variable let user = User.getCurrentUser()
class User: Object, Decodable {
#objc dynamic var firstName: String? = ""
#objc dynamic var lastName: String? = ""
#objc dynamic var email: String = ""
#objc dynamic var signedIn: Bool = false
override static func primaryKey() -> String? {
return "email"
}
private enum CodingKeys: String, CodingKey {
case email
case firstName
case lastName
}
}
extension User {
func updateUser(block: (User) -> ()) {
let realm = UserRealm.create()
try? realm.write {
block(self)
}
static func getCurrentUser() -> User? {
let realm = UserRealm.create()
return realm.objects(User.self).filter("signedIn == %#", true).first
}
}
fileprivate let currentSchema: UInt64 = 104
struct UserRealm {
static func create() -> Realm {
do {
return try Realm(configuration: config)
} catch {
print(error)
fatalError("Creating User Realm Failed")
}
}
static var config: Realm.Configuration {
let url = Realm.Configuration().fileURL!.deletingLastPathComponent().appendingPathComponent("Users.realm")
return Realm.Configuration(fileURL: url,
schemaVersion: currentSchema, migrationBlock: { migration, oldSchema in
print("Old Schema version =", oldSchema)
print("Current schema version =", currentSchema)
print("")
if oldSchema < currentSchema {
}
}, shouldCompactOnLaunch: { (totalBytes, usedBytes) -> Bool in
let oneHundredMB = 100 * 1024 * 1024
return (totalBytes > oneHundredMB) && (Double(usedBytes) / Double(totalBytes)) < 0.5
})
}
}