RealmCollection

Returns the index of the first object matching the query, or nil if no objects match.

This is only applicable to ordered collections, and will abort if the collection is unordered.

• Usage:

  obj.index(matching: { $0.fooCol < 456 })
  

Returns the index of the first object matching the given predicate, or nil if no objects match.

Returns a Results containing all objects matching the given predicate in the collection.

Registers a block to be called each time the collection changes.

The block will be asynchronously called with the initial results, and then called again after each write transaction which changes either any of the objects in the collection, or which objects are in the collection.

The change parameter that is passed to the block reports, in the form of indices within the collection, which of the objects were added, removed, or modified during each write transaction. See the RealmCollectionChange documentation for more information on the change information supplied and an example of how to use it to update a UITableView.

At the time when the block is called, the collection will be fully evaluated and up-to-date, and as long as you do not perform a write transaction on the same thread or explicitly call realm.refresh(), accessing it will never perform blocking work.

If no queue is given, notifications are delivered via the standard run loop, and so can’t be delivered while the run loop is blocked by other activity. If a queue is given, notifications are delivered to that queue instead. When notifications can’t be delivered instantly, multiple notifications may be coalesced into a single notification. This can include the notification with the initial collection.

For example, the following code performs a write transaction immediately after adding the notification block, so there is no opportunity for the initial notification to be delivered first. As a result, the initial notification will reflect the state of the Realm after the write transaction.

let dogs = realm.objects(Dog.self)
print("dogs.count: \(dogs?.count)") // => 0
let token = dogs.observe { changes in
    switch changes {
    case .initial(let dogs):
        // Will print "dogs.count: 1"
        print("dogs.count: \(dogs.count)")
        break
    case .update:
        // Will not be hit in this example
        break
    case .error:
        break
    }
}
try! realm.write {
    let dog = Dog()
    dog.name = "Rex"
    person.dogs.append(dog)
}
// end of run loop execution context

If no key paths are given, the block will be executed on any insertion, modification, or deletion for all object properties and the properties of any nested, linked objects. If a key path or key paths are provided, then the block will be called for changes which occur only on the provided key paths. For example, if:

class Dog: Object {
    @Persisted var name: String
    @Persisted var age: Int
    @Persisted var toys: List<Toy>
}
// ...
let dogs = realm.objects(Dog.self)

let token = dogs.observe(keyPaths: [\Dog.name]) { changes in
    switch changes {
    case .initial(let dogs):
       // ...
    case .update:
       // This case is hit:
       // - after the token is initialized
       // - when the name property of an object in the
       // collection is modified
       // - when an element is inserted or removed
       //   from the collection.
       // This block is not triggered:
       // - when a value other than name is modified on
       //   one of the elements.
    case .error:
        // ...
    }
}
// end of run loop execution context

• If the observed key path were [\Dog.toys.brand], then any insertion or deletion to the toys list on any of the collection’s elements would trigger the block. Changes to the brand value on any Toy that is linked to a Dog in this collection will trigger the block. Changes to a value other than brand on any Toy that is linked to a Dog in this collection would not trigger the block. Any insertion or removal to the Dog type collection being observed would also trigger a notification.

• If the above example observed the [\Dog.toys] key path, then any insertion, deletion, or modification to the toys list for any element in the collection would trigger the block. Changes to any value on any Toy that is linked to a Dog in this collection would not trigger the block. Any insertion or removal to the Dog type collection being observed would still trigger a notification.

You must retain the returned token for as long as you want updates to be sent to the block. To stop receiving updates, call invalidate() on the token.

Registers a block to be called each time the collection changes.

The block will be asynchronously called with an initial version of the collection, and then called again after each write transaction which changes either any of the objects in the collection, or which objects are in the collection.

The actor parameter passed to the block is the actor which you pass to this function. This parameter is required to isolate the callback to the actor.

The change parameter that is passed to the block reports, in the form of indices within the collection, which of the objects were added, removed, or modified after the previous notification. The collection field in the change enum will be isolated to the requested actor, and is safe to use within that actor only. See the RealmCollectionChange documentation for more information on the change information supplied and an example of how to use it to update a UITableView.

Once the initial notification is delivered, the collection will be fully evaluated and up-to-date, and accessing it will never perform any blocking work. This guarantee holds only as long as you do not perform a write transaction on the same actor as notifications are being delivered to. If you do, accessing the collection before the next notification is delivered may need to rerun the query.

Notifications are delivered to the given actor’s executor. When notifications can’t be delivered instantly, multiple notifications may be coalesced into a single notification. This can include the notification with the initial collection: any writes which occur before the initial notification is delivered may not produce change notifications.

Adding, removing or assigning objects in the collection always produces a notification. By default, modifying the objects which a collection links to (and the objects which those objects link to, if applicable) will also report that index in the collection as being modified. If a non-empty array of keypaths is provided, then only modifications to those keypaths will mark the object as modified. For example:

class Dog: Object {
    @Persisted var name: String
    @Persisted var age: Int
    @Persisted var toys: List<Toy>
}

let dogs = realm.objects(Dog.self)
let token = await dogs.observe(keyPaths: ["name"], on: myActor) { actor, changes in
    switch changes {
    case .initial(let dogs):
        // Query has finished running and dogs can not be used without blocking
    case .update:
        // This case is hit:
        // - after the token is initialized
        // - when the name property of an object in the collection is modified
        // - when an element is inserted or removed from the collection.
        // This block is not triggered:
        // - when a value other than name is modified on one of the elements.
    case .error:
        // Can no longer happen but is left for backwards compatiblity
    }
}

• If the observed key path were ["toys.brand"], then any insertion or deletion to the toys list on any of the collection’s elements would trigger the block. Changes to the brand value on any Toy that is linked to a Dog in this collection will trigger the block. Changes to a value other than brand on any Toy that is linked to a Dog in this collection would not trigger the block. Any insertion or removal to the Dog type collection being observed would also trigger a notification.
• If the above example observed the ["toys"] key path, then any insertion, deletion, or modification to the toys list for any element in the collection would trigger the block. Changes to any value on any Toy that is linked to a Dog in this collection would not trigger the block. Any insertion or removal to the Dog type collection being observed would still trigger a notification.

You must retain the returned token for as long as you want updates to be sent to the block. To stop receiving updates, call invalidate() on the token.

Returns a Results containing distinct objects based on the specified key paths

Registers a block to be called each time the collection changes.

The block will be asynchronously called with the initial results, and then called again after each write transaction which changes either any of the objects in the collection, or which objects are in the collection.

The change parameter that is passed to the block reports, in the form of indices within the collection, which of the objects were added, removed, or modified during each write transaction. See the RealmCollectionChange documentation for more information on the change information supplied and an example of how to use it to update a UITableView.

At the time when the block is called, the collection will be fully evaluated and up-to-date, and as long as you do not perform a write transaction on the same thread or explicitly call realm.refresh(), accessing it will never perform blocking work.

If no queue is given, notifications are delivered via the standard run loop, and so can’t be delivered while the run loop is blocked by other activity. If a queue is given, notifications are delivered to that queue instead. When notifications can’t be delivered instantly, multiple notifications may be coalesced into a single notification. This can include the notification with the initial collection.

For example, the following code performs a write transaction immediately after adding the notification block, so there is no opportunity for the initial notification to be delivered first. As a result, the initial notification will reflect the state of the Realm after the write transaction.

let dogs = realm.objects(Dog.self)
print("dogs.count: \(dogs?.count)") // => 0
let token = dogs.observe { changes in
    switch changes {
    case .initial(let dogs):
        // Will print "dogs.count: 1"
        print("dogs.count: \(dogs.count)")
        break
    case .update:
        // Will not be hit in this example
        break
    case .error:
        break
    }
}
try! realm.write {
    let dog = Dog()
    dog.name = "Rex"
    person.dogs.append(dog)
}
// end of run loop execution context

If no key paths are given, the block will be executed on any insertion, modification, or deletion for all object properties and the properties of any nested, linked objects. If a key path or key paths are provided, then the block will be called for changes which occur only on the provided key paths. For example, if:

class Dog: Object {
    @Persisted var name: String
    @Persisted var age: Int
    @Persisted var toys: List<Toy>
}
// ...
let dogs = realm.objects(Dog.self)

let token = dogs.observe(keyPaths: [\Dog.name]) { changes in
    switch changes {
    case .initial(let dogs):
       // ...
    case .update:
       // This case is hit:
       // - after the token is initialized
       // - when the name property of an object in the
       // collection is modified
       // - when an element is inserted or removed
       //   from the collection.
       // This block is not triggered:
       // - when a value other than name is modified on
       //   one of the elements.
    case .error:
        // ...
    }
}
// end of run loop execution context

• If the observed key path were [\Dog.toys.brand], then any insertion or deletion to the toys list on any of the collection’s elements would trigger the block. Changes to the brand value on any Toy that is linked to a Dog in this collection will trigger the block. Changes to a value other than brand on any Toy that is linked to a Dog in this collection would not trigger the block. Any insertion or removal to the Dog type collection being observed would also trigger a notification.

• If the above example observed the [\Dog.toys] key path, then any insertion, deletion, or modification to the toys list for any element in the collection would trigger the block. Changes to any value on any Toy that is linked to a Dog in this collection would not trigger the block. Any insertion or removal to the Dog type collection being observed would still trigger a notification.

You must retain the returned token for as long as you want updates to be sent to the block. To stop receiving updates, call invalidate() on the token.

Registers a block to be called each time the collection changes.

The block will be asynchronously called with an initial version of the collection, and then called again after each write transaction which changes either any of the objects in the collection, or which objects are in the collection.

The actor parameter passed to the block is the actor which you pass to this function. This parameter is required to isolate the callback to the actor.

The change parameter that is passed to the block reports, in the form of indices within the collection, which of the objects were added, removed, or modified after the previous notification. The collection field in the change enum will be isolated to the requested actor, and is safe to use within that actor only. See the RealmCollectionChange documentation for more information on the change information supplied and an example of how to use it to update a UITableView.

Once the initial notification is delivered, the collection will be fully evaluated and up-to-date, and accessing it will never perform any blocking work. This guarantee holds only as long as you do not perform a write transaction on the same actor as notifications are being delivered to. If you do, accessing the collection before the next notification is delivered may need to rerun the query.

Notifications are delivered to the given actor’s executor. When notifications can’t be delivered instantly, multiple notifications may be coalesced into a single notification. This can include the notification with the initial collection: any writes which occur before the initial notification is delivered may not produce change notifications.

Adding, removing or assigning objects in the collection always produces a notification. By default, modifying the objects which a collection links to (and the objects which those objects link to, if applicable) will also report that index in the collection as being modified. If a non-empty array of keypaths is provided, then only modifications to those keypaths will mark the object as modified. For example:

class Dog: Object {
    @Persisted var name: String
    @Persisted var age: Int
    @Persisted var toys: List<Toy>
}

let dogs = realm.objects(Dog.self)
let token = await dogs.observe(keyPaths: [\.name], on: myActor) { actor, changes in
    switch changes {
    case .initial(let dogs):
        // Query has finished running and dogs can not be used without blocking
    case .update:
        // This case is hit:
        // - after the token is initialized
        // - when the name property of an object in the collection is modified
        // - when an element is inserted or removed from the collection.
        // This block is not triggered:
        // - when a value other than name is modified on one of the elements.
    case .error:
        // Can no longer happen but is left for backwards compatiblity
    }
}

• If the observed key path were [\.toys.brand], then any insertion or deletion to the toys list on any of the collection’s elements would trigger the block. Changes to the brand value on any Toy that is linked to a Dog in this collection will trigger the block. Changes to a value other than brand on any Toy that is linked to a Dog in this collection would not trigger the block. Any insertion or removal to the Dog type collection being observed would also trigger a notification.
• If the above example observed the [\.toys] key path, then any insertion, deletion, or modification to the toys list for any element in the collection would trigger the block. Changes to any value on any Toy that is linked to a Dog in this collection would not trigger the block. Any insertion or removal to the Dog type collection being observed would still trigger a notification.

You must retain the returned token for as long as you want updates to be sent to the block. To stop receiving updates, call invalidate() on the token.