LinkingObjects

The type of the objects represented by the linking objects.

The Realm which manages the linking objects, or nil if the linking objects are unmanaged.

Indicates if the linking objects are no longer valid.

The linking objects become invalid if invalidate() is called on the containing realm instance.

An invalidated linking objects can be accessed, but will always be empty.

The number of linking objects.

Creates an instance of a LinkingObjects. This initializer should only be called when declaring a property on a Realm model.

A human-readable description of the objects represented by the linking objects.

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

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

Returns the object at the given index.

Returns the first object in the linking objects, or nil if the linking objects are empty.

Returns the last object in the linking objects, or nil if the linking objects are empty.

Returns an array containing the objects in the linking objects at the indexes specified by a given index set.

Returns an Array containing the results of invoking valueForKey(_:) with key on each of the linking objects.

Returns an Array containing the results of invoking valueForKeyPath(_:) with keyPath on each of the linking objects.

Invokes setValue(_:forKey:) on each of the linking objects using the specified value and key.

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

Returns a Results containing all the linking objects, but sorted.

Objects are sorted based on the values of the given key path. For example, to sort a collection of Students from youngest to oldest based on their age property, you might call students.sorted(byKeyPath: "age", ascending: true).

Returns a Results containing all the linking objects, but sorted.

Returns the minimum (lowest) value of the given property among all the linking objects, or nil if the linking objects are empty.

Returns the maximum (highest) value of the given property among all the linking objects, or nil if the linking objects are empty.

Returns the sum of the values of a given property over all the linking objects.

Returns the average value of a given property over all the linking objects, or nil if the linking objects are empty.

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(originProperty: "handlers")
    var dogs: LinkingObjects<Dog>
}
class Dog: Object {
    @Persisted var name: String
    @Persisted var handlers: List<Person>
}
// ...
let dogs = person.dogs
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

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(originProperty: "handlers")
    var dogs: LinkingObjects<Dog>
}
class Dog: Object {
    @Persisted var name: String
    @Persisted var handlers: List<Person>
}
// ...
let dogs = person.dogs
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 Person: Object {
    @Persisted(originProperty: "handlers")
    var dogs: LinkingObjects<Dog>
}
class Dog: Object {
    @Persisted var name: String
    @Persisted var age: Int
    @Persisted var toys: List<Toy>
    @Persisted var handlers: List<Person>
}
// ...
let dogs = person.dogs
let token = dogs.observe(keyPaths: ["name"]) { changes in
    switch changes {
    case .initial(let dogs):
       // ...
    case .update:
       // This case is hit:
       // - after the token is intialized
       // - 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 ["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.

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(originProperty: "handlers")
    var dogs: LinkingObjects<Dog>
}
class Dog: Object {
    @Persisted var name: String
    @Persisted var handlers: List<Person>
}
// ...
let dogs = person.dogs
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 Person: Object {
    @Persisted(originProperty: "handlers")
    var dogs: LinkingObjects<Dog>
}
class Dog: Object {
    @Persisted var name: String
    @Persisted var age: Int
    @Persisted var toys: List<Toy>
    @Persisted var handlers: List<Person>
}
// ...
let dogs = person.dogs
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 intialized
       // - 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.

Returns if this collection is frozen.

Returns a frozen (immutable) snapshot of this collection.

The frozen copy is an immutable collection which contains the same data as this collection currently contains, but will not update when writes are made to the containing Realm. Unlike live collections, frozen collections can be accessed from any thread.

Returns a live version of this frozen collection.

This method resolves a reference to a live copy of the same frozen collection. If called on a live collection, will return itself.

A publisher that emits Void each time the collection changes.

Despite the name, this actually emits after the collection has changed.

Returns an iterator that yields successive elements in the linking objects.

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().