RLMArray

@interface RLMArray<RLMObjectType> : 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). In addition, the property can be declared using Objective-C generics for better compile-time type safety.

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 managed RLMObject (RLMArrays on unmanaged 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

  • The number of objects in the array.

    Declaration

    Objective-C

    @property (readonly, assign, nonatomic) NSUInteger count;
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  • The type of the objects in the array.

    Declaration

    Objective-C

    @property (readonly, assign, nonatomic) RLMPropertyType type;
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  • Indicates whether the objects in the collection can be nil.

    Declaration

    Objective-C

    @property (readonly, getter=isOptional, nonatomic) BOOL optional;
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  • The class name of the objects contained in the array.

    Will be nil if type is not RLMPropertyTypeObject.

    Declaration

    Objective-C

    @property (readonly, copy, nonatomic, nullable) NSString *objectClassName;
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  • The Realm which manages the array. Returns nil for unmanaged arrays.

    Declaration

    Objective-C

    @property (readonly, nonatomic, nullable) RLMRealm *realm;
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  • Indicates if the 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 object of the type contained in the array.

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  • Returns the first object in the array.

    Returns nil if called on an empty array.

    Declaration

    Objective-C

    - (nullable RLMObjectType)firstObject;

    Return Value

    An object of the type contained in the array.

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  • Returns the last object in the array.

    Returns nil if called on an empty array.

    Declaration

    Objective-C

    - (nullable RLMObjectType)lastObject;

    Return Value

    An object of the type contained in the array.

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Adding, Removing, and Replacing Objects in an Array

  • Adds an object to the end of the array.

    Warning

    This method may only be called during a write transaction.

    Declaration

    Objective-C

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

    Parameters

    object

    An object of the type contained in the array.
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  • Adds an array of objects to the end of the array.

    Warning

    This method may 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 the array.
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  • Inserts an object at the given index.

    Throws an exception if the index exceeds the bounds of the array.

    Warning

    This method may only be called during a write transaction.

    Declaration

    Objective-C

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

    Parameters

    anObject

    An object of the type contained in the array.
    index

    The index at which to insert the object.
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  • Removes an object at the given index.

    Throws an exception if the index exceeds the bounds of the array.

    Warning

    This method may 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 the array.

    This is a no-op if the array is already empty.

    Warning

    This method may only be called during a write transaction.

    Declaration

    Objective-C

    - (void)removeLastObject;
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  • Removes all objects from the array.

    Warning

    This method may 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 if the index exceeds the bounds of the array.

    Warning

    This method may only be called during a write transaction.

    Declaration

    Objective-C

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

    Parameters

    index

    The 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 if the index exceeds the bounds of the array.

    Warning

    This method may 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 indices.

    Throws an exception if either index exceeds the bounds of the array.

    Warning

    This method may only be called during a write transaction.

    Declaration

    Objective-C

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

    Parameters

    index1

    The index of the object which should replace the object at index index2.
    index2

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

  • Returns the index of an object in the array.

    Returns NSNotFound if the object is not found in the array.

    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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  • Returns the index of the first object in the array matching the predicate.

    Declaration

    Objective-C

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

    Parameters

    predicateFormat

    A predicate format string, optionally followed by a variable number of arguments.

    Return Value

    The index of the object, or NSNotFound if the object is not found in the array.

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  • Returns the index of the first object in the array matching the predicate.

    Declaration

    Objective-C

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

    Parameters

    predicate

    The predicate with which to filter the objects.

    Return Value

    The index of the object, or NSNotFound if the object is not found in the array.

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  • Returns all the objects matching the given predicate in the array.

    Declaration

    Objective-C

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

    Parameters

    predicateFormat

    A predicate format string, optionally followed by a variable number of arguments.

    Return Value

    An RLMResults of objects that match the given predicate.

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  • Returns all the objects matching the given predicate in the array.

    Declaration

    Objective-C

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

    Parameters

    predicate

    The predicate with which to filter the objects.

    Return Value

    An RLMResults of objects that match the given predicate

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  • Returns a sorted RLMResults from the array.

    Declaration

    Objective-C

    - (nonnull RLMResults<RLMObjectType> *)
    sortedResultsUsingKeyPath:(nonnull NSString *)keyPath
                    ascending:(BOOL)ascending;

    Parameters

    keyPath

    The key path to sort by.
    ascending

    The direction to sort in.

    Return Value

    An RLMResults sorted by the specified key path.

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  • Returns a sorted RLMResults from the array.

    Declaration

    Objective-C

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

    Parameters

    properties

    An array of RLMSortDescriptors to sort by.

    Return Value

    An RLMResults sorted by the specified properties.

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Notifications

  • Registers a block to be called each time the array 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 changes parameter will be nil the first time the block is called. 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 the 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 Realm 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 addNotificationBlock(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 -invalidate on the token.

    Warning

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

    Warning

    This method may only be called on a managed array.

    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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Aggregating Property Values

  • Returns the minimum (lowest) value of the given property among all the objects in the array.

    NSNumber *min = [object.arrayProperty minOfProperty:@"age"];

    Warning

    You cannot use this method on RLMObject, RLMArray, and NSData properties.

    Declaration

    Objective-C

    - (nullable id)minOfProperty:(nonnull NSString *)property;

    Parameters

    property

    The property whose minimum value is desired. Only properties of types int, float, double, and NSDate are supported.

    Return Value

    The minimum value of the property, or nil if the array is empty.

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  • Returns the maximum (highest) value of the given property among all the objects in the array.

    NSNumber *max = [object.arrayProperty maxOfProperty:@"age"];

    Warning

    You cannot use this method on RLMObject, RLMArray, and NSData properties.

    Declaration

    Objective-C

    - (nullable id)maxOfProperty:(nonnull NSString *)property;

    Parameters

    property

    The property whose maximum value is desired. Only properties of types int, float, double, and NSDate are supported.

    Return Value

    The maximum value of the property, or nil if the array is empty.

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  • Returns the sum of the values of a given property over all the objects in the array.

    NSNumber *sum = [object.arrayProperty sumOfProperty:@"age"];

    Warning

    You cannot use this method on RLMObject, RLMArray, and NSData properties.

    Declaration

    Objective-C

    - (nonnull NSNumber *)sumOfProperty:(nonnull NSString *)property;

    Parameters

    property

    The property whose values should be summed. Only properties of types int, float, and double are supported.

    Return Value

    The sum of the given property.

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  • Returns the average value of a given property over the objects in the array.

    NSNumber *average = [object.arrayProperty averageOfProperty:@"age"];

    Warning

    You cannot use this method on RLMObject, RLMArray, and NSData properties.

    Declaration

    Objective-C

    - (nullable NSNumber *)averageOfProperty:(nonnull NSString *)property;

    Parameters

    property

    The property whose average value should be calculated. Only properties of types int, float, and double are supported.

    Return Value

    The average value of the given property, or nil if the array is empty.

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Unavailable Methods

  • Unavailable

    RLMArrays cannot be created directly

    -[RLMArray init] is not available because RLMArrays cannot be created directly. RLMArray properties on RLMObjects are lazily created when accessed.

    Declaration

    Objective-C

    - (nonnull instancetype)init;
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  • Unavailable

    RLMArrays cannot be created directly

    +[RLMArray new] is not available because RLMArrays cannot be created directly. RLMArray properties on RLMObjects are lazily created when accessed.

    Declaration

    Objective-C

    + (nonnull instancetype)new;
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