RealmSectionedResult

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

The block will be asynchronously called with the initial sectioned results collection, and then called again after each write transaction which changes either any of the objects in the sectioned results collection, or which objects are in the sectioned results 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 SectionedResultsChange 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 sectioned results 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)
let sectionedResults = dogs.sectioned(by: \.age, ascending: true)
print("sectionedResults.count: \(sectionedResults?.count)") // => 0
let token = sectionedResults.observe { changes in
    switch changes {
    case .initial(let sectionedResults):
        // Will print "sectionedResults.count: 1"
        print("sectionedResults.count: \(sectionedResults.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 sectionedResults = dogs.sectioned(by: \.age, ascending: true)
let token = sectionedResults.observe(keyPaths: ["name"]) { changes in
    switch changes {
    case .initial(let sectionedResults):
       // ...
    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 ["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.

• Any modification to the section key path property which results in the object changing position in the section, or changing section entirely will 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 sectioned results collection changes.

The block will be asynchronously called with the initial sectioned results collection, and then called again after each write transaction which changes either any of the objects in the sectioned results collection, or which objects are in the sectioned results 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 SectionedResultsChange 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 sectioned results 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)
let sectionedResults = dogs.sectioned(by: \.age, ascending: true)
print("sectionedResults.count: \(sectionedResults?.count)") // => 0
let token = sectionedResults.observe { changes in
    switch changes {
    case .initial(let sectionedResults):
        // Will print "sectionedResults.count: 1"
        print("sectionedResults.count: \(sectionedResults.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 sectionedResults = dogs.sectioned(by: \.age, ascending: true)
let token = sectionedResults.observe(keyPaths: ["name"]) { changes in
    switch changes {
    case .initial(let sectionedResults):
       // ...
    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 ["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.

• Any modification to the section key path property which results in the object changing position in the section, or changing section entirely will 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.