RealmKeyedCollection

A homogenous key-value collection of Objects which can be retrieved, filtered, sorted, and operated upon.

  • Key

    The type of key associated with this collection

  • The type of value associated with this collection.

Properties

  • The Realm which manages the map, or nil if the map is unmanaged.

  • Indicates if the map can no longer be accessed.

  • Returns the number of key-value pairs in this map.

  • A human-readable description of the objects contained in the Map.

Mutation

  • Updates the value stored in the dictionary for the given key, or adds a new key-value pair if the key does not exist.

    Note

    Note:If the value being added to the dictionary is an unmanaged object and the dictionary is managed then that unmanaged object will be added to the Realm.

    Warning

    This method may only be called during a write transaction.

  • Removes the given key and its associated object, only if the key exists in the dictionary. If the key does not exist, the dictionary will not be modified.

    Warning

    This method may only be called during a write transaction.
  • Removes all objects from the dictionary. The objects are not removed from the Realm that manages them.

    Warning

    This method may only be called during a write transaction.
  • Returns the value for a given key, or sets a value for a key should the subscript be used for an assign.

    Note

    Note:If the value being added to the dictionary is an unmanaged object and the dictionary is managed then that unmanaged object will be added to the Realm.

    Note

    Note:If the value being assigned for a key is nil then that key will be removed from the dictionary.

    Warning

    This method may only be called during a write transaction.

KVC

  • Returns a type of Value for a specified key if it exists in the map.

    Note that when using key-value coding, the key must be a string.

  • Returns a type of Value for a specified key if it exists in the map.

  • Adds a given key-value pair to the dictionary or updates a given key should it already exist.

    Warning

    This method can only be called during a write transaction.

Filtering

  • Returns a Results containing all matching values in the dictionary with the given predicate.

    Note

    This will return the values in the dictionary, and not the key-value pairs.

  • Returns a Boolean value indicating whether the Map contains the key-value pair satisfies the given predicate

Sorting

  • sorted(ascending:) Default implementation

    Returns a Results containing the objects in the dictionary, but sorted.

    Objects are sorted based on their values. For example, to sort a dictionary of Dates from neweset to oldest based, you might call dates.sorted(ascending: true).

    Default Implementation

    Returns a Results containing the objects in the collection, but sorted.

    Objects are sorted based on their values. For example, to sort a collection of Dates from neweset to oldest based, you might call dates.sorted(ascending: true).

  • Returns a Results containing the objects in the dictionary, but sorted.

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

    Warning

    Dictionaries may only be sorted by properties of boolean, Date, NSDate, single and double-precision floating point, integer, and string types.

  • Returns a Results containing the objects in the dictionary, but sorted.

    Warning

    Dictionaries may only be sorted by properties of boolean, Date, NSDate, single and double-precision floating point, integer, and string types.

  • Returns all of the keys in this dictionary.

  • Returns all of the values in the dictionary.

Aggregate Operations

  • Returns the minimum (lowest) value of the given property among all the objects in the collection, or nil if the dictionary is empty.

    Warning

    Only a property whose type conforms to the MinMaxType protocol can be specified.

  • Returns the maximum (highest) value of the given property among all the objects in the dictionary, or nil if the dictionary is empty.

    Warning

    Only a property whose type conforms to the MinMaxType protocol can be specified.

  • Returns the sum of the given property for objects in the dictionary, or nil if the dictionary is empty.

    Warning

    Only names of properties of a type conforming to the AddableType protocol can be used.

  • Returns the average value of a given property over all the objects in the dictionary, or nil if the dictionary is empty.

    Warning

    Only a property whose type conforms to the AddableType protocol can be specified.

Notifications

  • Registers a block to be called each time the dictionary changes.

    The block will be asynchronously called with the initial dictionary, and then called again after each write transaction which changes either any of the keys or values in the dictionary.

    The change parameter that is passed to the block reports, in the form of keys within the dictionary, which of the key-value pairs were added, removed, or modified during each write transaction.

    At the time when the block is called, the dictionary 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 myStringMap = myObject.stringMap
    print("myStringMap.count: \(myStringMap?.count)") // => 0
    let token = myStringMap.observe { changes in
        switch changes {
        case .initial(let myStringMap):
            // Will print "myStringMap.count: 1"
            print("myStringMap.count: \(myStringMap.count)")
           print("Dog Name: \(myStringMap["nameOfDog"])") // => "Rex"
            break
        case .update:
            // Will not be hit in this example
            break
        case .error:
            break
        }
    }
    try! realm.write {
        myStringMap["nameOfDog"] = "Rex"
    }
    // 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.

    Warning

    This method cannot be called during a write transaction, or when the containing Realm is read-only.
  • Registers a block to be called each time the dictionary changes.

    The block will be asynchronously called with the initial dictionary, and then called again after each write transaction which changes either any of the keys or values in the dictionary.

    The change parameter that is passed to the block reports, in the form of keys within the dictionary, which of the key-value pairs were added, removed, or modified during each write transaction.

    At the time when the block is called, the dictionary 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 myStringMap = myObject.stringMap
    print("myStringMap.count: \(myStringMap?.count)") // => 0
    let token = myStringMap.observe { changes in
        switch changes {
        case .initial(let myStringMap):
            // Will print "myStringMap.count: 1"
            print("myStringMap.count: \(myStringMap.count)")
           print("Dog Name: \(myStringMap["nameOfDog"])") // => "Rex"
            break
        case .update:
            // Will not be hit in this example
            break
        case .error:
            break
        }
    }
    try! realm.write {
        myStringMap["nameOfDog"] = "Rex"
    }
    // 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 = myObject.mapOfDogs
    let token = dogs.observe(keyPaths: ["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 ["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.

    Note

    Multiple notification tokens on the same object which filter for separate key paths do not filter exclusively. If one key path change is satisfied for one notification token, then all notification token blocks for that object will execute.

    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.

    Warning

    This method cannot be called during a write transaction, or when the containing Realm is read-only.

    Note

    The keyPaths parameter refers to object properties of the collection type and does not refer to particular key/value pairs within the collection.

Frozen Objects

  • 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.

    Warning

    This method cannot be called during a write transaction, or when the containing Realm is read-only.

    Warning

    Holding onto a frozen collection for an extended period while performing write transaction on the Realm may result in the Realm file growing to large sizes. See Realm.Configuration.maximumNumberOfActiveVersions for more information.
  • Returns a live (mutable) 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.

  • min(of:) Extension method

    Returns the minimum (lowest) value of the given property among all the objects in the collection, or nil if the collection is empty.

    Warning

    Only a property whose type conforms to the MinMaxType protocol can be specified.

  • max(of:) Extension method

    Returns the maximum (highest) value of the given property among all the objects in the collection, or nil if the collection is empty.

    Warning

    Only a property whose type conforms to the MinMaxType protocol can be specified.

  • sum(of:) Extension method

    Returns the sum of the given property for objects in the collection, or nil if the collection is empty.

    Warning

    Only names of properties of a type conforming to the AddableType protocol can be used.

  • average(of:) Extension method

    Returns the average value of a given property over all the objects in the collection, or nil if the collection is empty.

    Warning

    Only a property whose type conforms to the AddableType protocol can be specified.

Sortable

  • sorted(by:ascending:) Extension method

    Returns a Results containing the objects in the collection, 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).

    Warning

    Collections may only be sorted by properties of boolean, Date, NSDate, single and double-precision floating point, integer, and string types.

  • min() Extension method

    Returns the minimum (lowest) value of the collection, or nil if the collection is empty.

  • max() Extension method

    Returns the maximum (highest) value of the collection, or nil if the collection is empty.

  • sum() Extension method

    Returns the sum of the values in the collection, or nil if the collection is empty.

  • average() Extension method

    Returns the average of all of the values in the collection.