RealmKeyedCollection
A homogenous key-value collection of Object
s which can be retrieved, filtered, sorted, and operated upon.
-
The type of key associated with this collection
-
The type of value associated with this collection.
-
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.
-
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.
-
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.
-
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
-
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
Date
s from neweset to oldest based, you might calldates.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
Date
s from neweset to oldest based, you might calldates.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
Student
s from youngest to oldest based on theirage
property, you might callstudents.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.
-
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.
-
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 thetoys
list on any of the collection’s elements would trigger the block. Changes to thebrand
value on anyToy
that is linked to aDog
in this collection will trigger the block. Changes to a value other thanbrand
on anyToy
that is linked to aDog
in this collection would not trigger the block. Any insertion or removal to theDog
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 thetoys
list for any element in the collection would trigger the block. Changes to any value on anyToy
that is linked to aDog
in this collection would not trigger the block. Any insertion or removal to theDog
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.
- If the observed key path were
-
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. SeeRealm.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.
-
sorted(by:
Extension methodascending: ) 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
Student
s from youngest to oldest based on theirage
property, you might callstudents.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 methodReturns the minimum (lowest) value of the collection, or
nil
if the collection is empty. -
max()
Extension methodReturns the maximum (highest) value of the collection, or
nil
if the collection is empty. -
sum()
Extension methodReturns the sum of the values in the collection, or
nil
if the collection is empty. -
average()
Extension methodReturns the average of all of the values in the collection.