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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 value

  • If the dictionary's value is optional, you can set the value of the key to nil to 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 Use Realm with Actors page shows how you might delete an object in an actor-isolated realm:

func deleteTodo(id: ObjectId) async throws {
    try await realm.asyncWrite {
        let todoToDelete = realm.object(ofType: Todo.self, forPrimaryKey: id)
        realm.delete(todoToDelete!)
    }
}

And you might perform this deletion using Swift's async syntax:

let actor = try await RealmActor()
let todoId = await actor.getObjectId(forTodoNamed: "Keep Mr. Frodo safe from that Gollum")
try await actor.deleteTodo(id: todoId)
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 Use Realm with Actors - Swift SDK.

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