RLMArray

@interface RLMArray <RLMObjectType : RLMObject *> : NSObject<RLMCollection,NSFastEnumeration>

RLMArray is the container type in Realm used to define to-many relationships.

Unlike an NSArray, RLMArrays hold a single type, specified by the objectClassName property. This is referred to in these docs as the “type” of the array.

When declaring an RLMArray property, the type must be marked as conforming to a protocol by the same name as the objects it should contain (see the RLM_ARRAY_TYPE macro). RLMArray properties can also use Objective‑C generics if available. For example:

RLM_ARRAY_TYPE(ObjectType)
...
@property RLMArray<ObjectType *><ObjectType> *arrayOfObjectTypes;

RLMArrays can be queried with the same predicates as RLMObject and RLMResults.

RLMArrays cannot be created directly. RLMArray properties on RLMObjects are lazily created when accessed, or can be obtained by querying a Realm.

Key-Value Observing

RLMArray supports array key-value observing on RLMArray properties on RLMObject subclasses, and the invalidated property on RLMArray instances themselves is key-value observing compliant when the RLMArray is attached to a persisted RLMObject (RLMArrays on standalone RLMObjects will never become invalidated).

Because RLMArrays are attached to the object which they are a property of, they do not require using the mutable collection proxy objects from -mutableArrayValueForKey: or KVC-compatible mutation methods on the containing object. Instead, you can call the mutation methods on the RLMArray directly.

Properties

  • Number of objects in the array.

    Declaration

    Objective‑C

    @property (readonly, assign, nonatomic) NSUInteger count;
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  • The class name (i.e. type) of the RLMObjects contained in this RLMArray.

    Declaration

    Objective‑C

    @property (readonly, copy, nonatomic) NSString *_Nonnull objectClassName;
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  • The Realm in which this array is persisted. Returns nil for standalone arrays.

    Declaration

    Objective‑C

    @property (readonly, nonatomic, nullable) RLMRealm *realm;
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  • Indicates if an array can no longer be accessed.

    Declaration

    Objective‑C

    @property (readonly, getter=isInvalidated, nonatomic) BOOL invalidated;
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Accessing Objects from an Array

  • Returns the object at the index specified.

    Declaration

    Objective‑C

    - (nonnull RLMObjectType)objectAtIndex:(NSUInteger)index;

    Parameters

    index

    The index to look up.

    Return Value

    An RLMObject of the type contained in this RLMArray.

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  • Returns the first object in the array.

    Returns nil if called on an empty RLMArray.

    Declaration

    Objective‑C

    - (nullable RLMObjectType)firstObject;

    Return Value

    An RLMObject of the type contained in this RLMArray.

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  • Returns the last object in the array.

    Returns nil if called on an empty RLMArray.

    Declaration

    Objective‑C

    - (nullable RLMObjectType)lastObject;

    Return Value

    An RLMObject of the type contained in this RLMArray.

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Adding, Removing, and Replacing Objects in an Array

  • Adds an object to the end of the array.

    Warning

    This method can only be called during a write transaction.

    Declaration

    Objective‑C

    - (void)addObject:(nonnull RLMObjectType)object;

    Parameters

    object

    An RLMObject of the type contained in this RLMArray.
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  • Adds an array of objects at the end of the array.

    Warning

    This method can only be called during a write transaction.

    Declaration

    Objective‑C

    - (void)addObjects:(nonnull id<NSFastEnumeration>)objects;

    Parameters

    objects

    An enumerable object such as NSArray or RLMResults which contains objects of the same class as this RLMArray.
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  • Inserts an object at the given index.

    Throws an exception when the index exceeds the bounds of this RLMArray.

    Warning

    This method can only be called during a write transaction.

    Declaration

    Objective‑C

    - (void)insertObject:(nonnull RLMObjectType)anObject atIndex:(NSUInteger)index;

    Parameters

    anObject

    An RLMObject of the type contained in this RLMArray.
    index

    The array index at which the object is inserted.
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  • Removes an object at a given index.

    Throws an exception when the index exceeds the bounds of this RLMArray.

    Warning

    This method can only be called during a write transaction.

    Declaration

    Objective‑C

    - (void)removeObjectAtIndex:(NSUInteger)index;

    Parameters

    index

    The array index identifying the object to be removed.
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  • Removes the last object in an RLMArray.

    Warning

    This method can only be called during a write transaction.

    Declaration

    Objective‑C

    - (void)removeLastObject;
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  • Removes all objects from an RLMArray.

    Warning

    This method can only be called during a write transaction.

    Declaration

    Objective‑C

    - (void)removeAllObjects;
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  • Replaces an object at the given index with a new object.

    Throws an exception when the index exceeds the bounds of this RLMArray.

    Warning

    This method can only be called during a write transaction.

    Declaration

    Objective‑C

    - (void)replaceObjectAtIndex:(NSUInteger)index
                  withObject:(nonnull RLMObjectType)anObject;

    Parameters

    index

    The array index of the object to be replaced.
    anObject

    An object (of the same type as returned from the objectClassName selector).
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  • Moves the object at the given source index to the given destination index.

    Throws an exception when the index exceeds the bounds of this RLMArray.

    Warning

    This method can only be called during a write transaction.

    Declaration

    Objective‑C

    - (void)moveObjectAtIndex:(NSUInteger)sourceIndex
                  toIndex:(NSUInteger)destinationIndex;

    Parameters

    sourceIndex

    The index of the object to be moved.
    destinationIndex

    The index to which the object at sourceIndex should be moved.
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  • Exchanges the objects in the array at given indexes.

    Throws an exception when either index exceeds the bounds of this RLMArray.

    Warning

    This method can only be called during a write transaction.

    Declaration

    Objective‑C

    - (void)exchangeObjectAtIndex:(NSUInteger)index1
            withObjectAtIndex:(NSUInteger)index2;

    Parameters

    index1

    The index of the object with which to replace the object at index index2.
    index2

    The index of the object with which to replace the object at index index1.
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Querying an Array

  • Gets the index of an object.

    Returns NSNotFound if the object is not found in this RLMArray.

    Declaration

    Objective‑C

    - (NSUInteger)indexOfObject:(nonnull RLMObjectType)object;

    Parameters

    object

    An object (of the same type as returned from the objectClassName selector).
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  • Gets the index of the first object matching the predicate.

    Declaration

    Objective‑C

    - (NSUInteger)indexOfObjectWhere:(nonnull NSString *)predicateFormat, ...;

    Parameters

    predicateFormat

    The predicate format string which can accept variable arguments.

    Return Value

    Index of object or NSNotFound if the object is not found in this RLMArray.

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  • Gets the index of the first object matching the predicate.

    Declaration

    Objective‑C

    - (NSUInteger)indexOfObjectWithPredicate:(nonnull NSPredicate *)predicate;

    Parameters

    predicate

    The predicate to filter the objects.

    Return Value

    Index of object or NSNotFound if the object is not found in this RLMArray.

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  • Get objects matching the given predicate in the RLMArray.

    Declaration

    Objective‑C

    - (nonnull RLMResults<RLMObjectType> *)objectsWhere:
    (nonnull NSString *)predicateFormat, ...;

    Parameters

    predicateFormat

    The predicate format string which can accept variable arguments.

    Return Value

    An RLMResults of objects that match the given predicate

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  • Get objects matching the given predicate in the RLMArray.

    Declaration

    Objective‑C

    - (nonnull RLMResults<RLMObjectType> *)objectsWithPredicate:
    (nonnull NSPredicate *)predicate;

    Parameters

    predicate

    The predicate to filter the objects.

    Return Value

    An RLMResults of objects that match the given predicate

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  • Get a sorted RLMResults from an RLMArray

    Declaration

    Objective‑C

    - (nonnull RLMResults<RLMObjectType> *)
sortedResultsUsingProperty:(nonnull NSString *)property
                 ascending:(BOOL)ascending;

    Parameters

    property

    The property name to sort by.
    ascending

    The direction to sort by.

    Return Value

    An RLMResults sorted by the specified property.

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  • Get a sorted RLMResults from an RLMArray

    Declaration

    Objective‑C

    - (nonnull RLMResults<RLMObjectType> *)sortedResultsUsingDescriptors:
    (nonnull NSArray *)properties;

    Parameters

    properties

    An array of RLMSortDescriptors to sort by.

    Return Value

    An RLMResults sorted by the specified properties.

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Notifications

  • Register a block to be called each time the RLMArray changes.

    The block will be asynchronously called with the initial array, and then called again after each write transaction which changes any of the objects in the array, which objects are in the results, or the order of the objects in the array.

    The change parameter will be nil the first time the block is called with the initial array. For each call after that, it will contain information about which rows in the array were added, removed or modified. If a write transaction did not modify any objects in this array, the block is not called at all. See the RLMCollectionChange documentation for information on how the changes are reported and an example of updating a UITableView.

    If an error occurs the block will be called with nil for the results parameter and a non-nil error. Currently the only errors that can occur are when opening the RLMRealm on the background worker thread.

    Notifications are delivered via the standard run loop, and so can’t be delivered while the run loop is blocked by other activity. When notifications can’t be delivered instantly, multiple notifications may be coalesced into a single notification. This can include the notification with the initial results. 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.

    Person *person = [[Person allObjectsInRealm:realm] firstObject];
NSLog(@"person.dogs.count: %zu", person.dogs.count); // => 0
self.token = [person.dogs RLMAddNotificationBlock(RLMArray<Dog *> *dogs,
                                                  RLMCollectionChange *changes,
                                                  NSError *error) {
    // Only fired once for the example
    NSLog(@"dogs.count: %zu", dogs.count) // => 1
}];
[realm transactionWithBlock:^{
    Dog *dog = [[Dog alloc] init];
    dog.name = @"Rex";
    [person.dogs addObject:dog];
}];
// end of run loop execution context

    You must retain the returned token for as long as you want updates to continue to be sent to the block. To stop receiving updates, call -stop on the token.

    Warning

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

    Warning

    This method can only be called on RLMArray object which has been add to or retrieved from a Realm.

    Declaration

    Objective‑C

    - (nonnull RLMNotificationToken *)addNotificationBlock:
    (nonnull void (^)(RLMArray<RLMObjectType> *_Nullable,
                      RLMCollectionChange *_Nullable, NSError *_Nullable))block;

    Parameters

    block

    The block to be called each time the array changes.

    Return Value

    A token which must be held for as long as you want updates to be delivered.

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Unavailable Methods

  • -[RLMArray init] is not available because RLMArrays cannot be created directly. RLMArray properties on RLMObjects are lazily created when accessed, or can be obtained by querying a Realm.

    Declaration

    Objective‑C

    - (nonnull instancetype)init;
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  • +[RLMArray new] is not available because RLMArrays cannot be created directly. RLMArray properties on RLMObjects are lazily created when accessed, or can be obtained by querying a Realm.

    Declaration

    Objective‑C

    + (nonnull instancetype) new;
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