CRUD - Delete - Swift SDK
On this page
- Delete Realm Objects
- About The Examples On This Page
- Delete an Object
- Delete Multiple Objects
- Delete an Object and Its Related Objects
- Delete All Objects of a Specific Type
- Delete All Objects in a Realm
- Delete Map Keys/Values
- Delete MutableSet Elements
- Delete the Value of an AnyRealmValue
- Delete an Object Asynchronously
Delete Realm Objects
Deleting Realm Objects must occur within write transactions. For more information about write trasactions, see: Transactions.
If you want to delete the Realm file itself, see: Delete a Realm.
Important
Do not use objects after delete
You cannot access or modify an object after you have deleted it from a realm. If you try to use a deleted object, Realm throws an error.
About The Examples On This Page
The examples on this page use the following models:
Delete an Object
Delete Multiple Objects
Delete an Object and Its Related Objects
Sometimes, you want to delete related objects when you delete the parent object. We call this a chaining delete. Realm does not delete the related objects for you. If you do not delete the objects yourself, they remain orphaned in your realm. Whether or not this is a problem depends on your application's needs.
The best way to delete dependent objects is to iterate through the dependencies and delete them before deleting the parent object.
Delete All Objects of a Specific Type
Delete All Objects in a Realm
Delete Map Keys/Values
You can delete map entries in a few ways:
Use
removeObject(for:)to remove the key and the valueIf the dictionary's value is optional, you can set the value of the key to
nilto keep the key.
let realm = try! Realm() // Find the dog we want to update let wolfie = realm.objects(Dog.self).where { $0.name == "Wolfie" }.first! // Delete an entry try! realm.write { // Use removeObject(for:) wolfie.favoriteParksByCity.removeObject(for: "New York") // Or assign `nil` to delete non-optional values. // If the value type were optional (e.g. Map<String, String?>) // this would assign `nil` to that entry rather than deleting it. wolfie.favoriteParksByCity["New York"] = nil } XCTAssertNil(wolfie.favoriteParksByCity["New York"])
Delete MutableSet Elements
You can delete specific elements from a MutableSet, or clear all of the elements from the set. If you are working with multiple sets, you can also remove elements in one set from the other set; see: Update a MutableSet Property.
let realm = try! Realm() // Record a dog's name and list of cities he has visited. let dog = Dog() dog.name = "Maui" let dogCitiesVisited = ["New York", "Boston", "Toronto"] try! realm.write { realm.add(dog) dog.citiesVisited.insert(objectsIn: dogCitiesVisited) } XCTAssertEqual(dog.citiesVisited.count, 3) // Later... we decide the dog didn't really visit Toronto // since the plane just stopped there for a layover. // Remove the element from the set. try! realm.write { dog.citiesVisited.remove("Toronto") } XCTAssertEqual(dog.citiesVisited.count, 2) // Or, in the case where the person entered the data for // the wrong dog, remove all elements from the set. try! realm.write { dog.citiesVisited.removeAll() } XCTAssertEqual(dog.citiesVisited.count, 0)
Delete the Value of an AnyRealmValue
To delete the value of an AnyRealmValue, set it to .none.
let realm = try! Realm() // Wolfie's companion is "Fluffy the Cat", represented by a string. // Fluffy has gone to visit friends for the summer, so Wolfie has no companion. let wolfie = realm.objects(Dog.self).where { $0.name == "Wolfie" }.first! try! realm.write { // You cannot set an AnyRealmValue to nil; you must set it to `.none`, instead. wolfie.companion = .none }
Delete an Object Asynchronously
You can use Swift concurrency features to asynchronously delete objects using an actor-isolated realm.
This function from the example RealmActor defined on the
Actor-Isolated Realms page shows how you might
delete an object in an actor-isolated realm:
func deleteTodo(todo: Todo) async throws { try await realm.asyncWrite { realm.delete(todo) } }
And you might perform this deletion using Swift's async syntax:
let actor = try await RealmActor() let todo = try await createObject(in: actor) print("Successfully created an object with id: \(todo._id)") let todoCount = await actor.count try await actor.deleteTodo(todo: todo) let updatedTodoCount = await actor.count if updatedTodoCount == todoCount - 1 { print("Successfully deleted the todo") }
This operation does not block or perform I/O on the calling thread. For more information about writing to realm using Swift concurrency features, refer to Actor-Isolated Realms - Swift SDK.