Adding new Object to existing List in Realm - ios

Question

I have two classes. First looks like that:
class Person: Object {
dynamic var owner: String?
var dogs: List<Dogs>()
}
and second class which looks like that:
class Dogs: Object {
dynamic var name: String?
dynamic var age: String?
}
and now in ViewController in 'viewDidLoad' I create object Person with empty List and save it in Realm
func viewDidLoad(){
let person = Person()
person.name = "Tomas"
try! realm.write {
realm.add(Person.self)
}
}
it works great and I can create Person, problem begins when I try to read this data in SecondViewController in ViewDidLoad doing it:
var persons: Results<Person>?
func viewDidLoad(){
persons = try! realm.allObjects()
}
and try to add new Dog to List doing it in button action:
#IBAction func addDog(){
let newDog = Dogs()
newDog.name = "Rex"
newDog.age = "2"
persons[0].dogs.append(newDog)
// in this place my application crashed
}
Here my app is crashing with an information: Can only add, remove, or create objects in a Realm in a write transaction - call beginWriteTransaction on an RLMRealm instance first. How can I add new Dog to List and how can I update person[0]?
I use SWIFT 3.0

Answer 1

The persons property is of type Results<Person>, which is a collection containing Person objects that are managed by a Realm. In order to modify a property of a managed object, such as appending a new element to a list property, you need to be within a write transaction.
try! realm.write {
persons[0].dogs.append(newDog)
}

Answer 2

Write something like this:
if let person = persons?[0] {
person.dogs.append(newDog)
}
try! realm.write {
realm.add(person, update: true)
}
Please check how are you getting realm. Each time you call defaultRealm, you are getting new realm.

Answer 3

Side Note: Besides adding the code inside the write transaction which solves your issue, you could query Person by name as follow...
#IBAction func addDog(){
let newDog = Dogs()
newDog.name = "Rex"
newDog.age = "2"
let personName = realm.objects(Person.self).filter("name = 'Tomas'").first!
try! realm.write {
personName.dogs.append(newDog)
}
}

Answer 4

Add object for Realm Database
class Task : Object {
#objc dynamic var id : Int = 0
#objc dynamic var name = ""
#objc dynamic var phone = ""
#objc dynamic var address = ""
}
#IBAction func buttonSave(_ sender: Any) {
let realm = try! Realm()
let user = Task()
user.id = 0
user.name = (txtName.text! as NSString) as String
user.phone = (txtPhone.text! as NSString) as String
user.address = (txtAddress.text! as NSString) as String
try! realm.write {
realm.add(user)
print("user:",user.name)
}
}