ProjectedCollection

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

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.

class Person: Object {
    @Persisted var dogs: List<Dog>
}
class PersonProjection: Projection<Person> {
    @Projected(\Person.dogs.projectTo.name) var dogsNames: ProjectedCollection<String>
}
// ...
let dogsNames = personProjection.dogsNames
print("dogsNames.count: \(dogsNames?.count)") // => 0
let token = dogsNames.observe { changes in
    switch changes {
    case .initial(let dogsNames):
        // Will print "dogsNames.count: 1"
        print("dogsNames.count: \(dogsNames.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

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 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.

class Person: Object {
    @Persisted var dogs: List<Dog>
}
class PersonProjection: Projection<Person> {
    @Projected(\Person.dogs.projectTo.name) var dogNames: ProjectedCollection<String>
}
// ...
let dogNames = personProjection.dogNames
print("dogNames.count: \(dogNames?.count)") // => 0
let token = dogs.observe { changes in
    switch changes {
    case .initial(let dogNames):
        // Will print "dogNames.count: 1"
        print("dogNames.count: \(dogNames.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 Person: Object {
    @Persisted var dogs: List<Dog>
}
class PersonProjection: Projection<Person> {
    @Projected(\Person.dogs.projectTo.name) var dogNames: ProjectedCollection<String>
}
// ...
let dogNames = personProjection.dogNames
let token = dogNames.observe(keyPaths: ["name"]) { changes in
    switch changes {
    case .initial(let dogNames):
       // ...
    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

Changes to any other value 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 the object at the given index (get), or replaces the object at the given index (set).

The position of the first element in a non-empty collection. Identical to endIndex in an empty collection.

The collection’s “past the end” position. endIndex is not a valid argument to subscript, and is always reachable from startIndex by zero or more applications of successor().

The Realm which manages the object.

Indicates if the collection can no longer be accessed.

A human-readable description of the object.

Returns the index of an object in the linking objects, or nil if the object is not present.