RLMResults

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

RLMResults is an auto-updating container type in Realm returned from object queries.

RLMResults can be queried with the same predicates as RLMObject and RLMArray and you can chain queries to further filter query results.

RLMResults always reflect the current state of the Realm on the current thread, including during write transactions on the current thread. The one exception to this is when using for...in fast enumeration, which will always enumerate over the objects which matched the query when the enumeration is begun, even if some of them are deleted or modified to be excluded by the filter during the enumeration.

RLMResults are initially lazily evaluated, and only run queries when the result of the query is requested. This means that chaining several temporary RLMResults to sort and filter your data does not perform any extra work processing the intermediate state.

Once the results have been evaluated or a notification block has been added, the results are eagerly kept up-to-date, with the work done to keep them up-to-date done on a background thread whenever possible.

RLMResults cannot be created directly.

Properties

  • Number of objects in the results.

    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 RLMResults.

    Declaration

    Objective‑C

    @property (readonly, copy, nonatomic) NSString *_Nonnull objectClassName;
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  • The Realm this RLMResults is associated with.

    Declaration

    Objective‑C

    @property (readonly, nonatomic) RLMRealm *_Nonnull realm;
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Accessing Objects from an RLMResults

  • 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 RLMResults.

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  • Returns the first object in the results.

    Returns nil if called on an empty RLMResults.

    Declaration

    Objective‑C

    - (nullable RLMObjectType)firstObject;

    Return Value

    An RLMObject of the type contained in this RLMResults.

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  • Returns the last object in the results.

    Returns nil if called on an empty RLMResults.

    Declaration

    Objective‑C

    - (nullable RLMObjectType)lastObject;

    Return Value

    An RLMObject of the type contained in this RLMResults.

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Querying Results

  • Gets the index of an object.

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

    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 RLMResults.

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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 RLMResults.

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  • Get objects matching the given predicate in the RLMResults.

    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 RLMResults.

    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 existing RLMResults sorted by a property.

    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 existing RLMResults sorted by an NSArrayofRLMSortDescriptor`s.

    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 RLMResults changes.

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

    The change parameter will be nil the first time the block is called with the initial results. For each call after that, it will contain information about which rows in the results were added, removed or modified. If a write transaction did not modify any objects in this results, 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.

    At the time when the block is called, the RLMResults object 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 -[RLMRealm refresh], accessing it will never perform blocking work.

    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.

    RLMResults<Dog *> *results = [Dog allObjects];
NSLog(@"dogs.count: %zu", dogs.count); // => 0
self.token = [results addNotificationBlock:^(RLMResults *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";
    [realm 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.

    Declaration

    Objective‑C

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

    Parameters

    block

    The block to be called with the evaluated results.

    Return Value

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

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Aggregating Property Values

  • Returns the minimum (lowest) value of the given property

    NSNumber *min = [results 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 to look for a minimum on. Only properties of type int, float, double and NSDate are supported.

    Return Value

    The minimum value for the property amongst objects in an RLMResults.

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  • Returns the maximum (highest) value of the given property of objects in an RLMResults

    NSNumber *max = [results 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 to look for a maximum on. Only properties of type int, float, double and NSDate are supported.

    Return Value

    The maximum value for the property amongst objects in an RLMResults

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  • Returns the sum of the given property for objects in an RLMResults.

    NSNumber *sum = [results 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 to calculate sum on. Only properties of type int, float and double are supported.

    Return Value

    The sum of the given property over all objects in an RLMResults.

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  • Returns the average of a given property for objects in an RLMResults.

    NSNumber *average = [results 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 to calculate average on. Only properties of type int, float and double are supported.

    Return Value

    The average for the given property amongst objects in an RLMResults. This will be of type double for both float and double properties.

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Unavailable Methods

  • -[RLMResults init] is not available because RLMResults cannot be created directly. RLMResults can be obtained by querying a Realm.

    Declaration

    Objective‑C

    - (nonnull instancetype)init;
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  • +[RLMResults new] is not available because RLMResults cannot be created directly. RLMResults can be obtained by querying a Realm.

    Declaration

    Objective‑C

    + (nonnull instancetype) new;
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