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NSHashTable Class Reference

Overview

NSHashTable is modeled after NSSet but provides different options, in particular to support weak relationships in a garbage-collected environment.

Tasks

Initialization

• – initWithOptions:capacity:
• – initWithPointerFunctions:capacity:

Convenience Constructors

• + hashTableWithOptions:
• + hashTableWithWeakObjects

Accessing Content

• – allObjects
• – anyObject
• – containsObject:
• – count
• – member:
• – objectEnumerator
• – setRepresentation

Manipulating Membership

• – addObject:
• – removeAllObjects
• – removeObject:

Comparing Hash Tables

• – intersectsHashTable:
• – isEqualToHashTable:
• – isSubsetOfHashTable:

Set Functions

• – intersectHashTable:
• – minusHashTable:
• – unionHashTable:

Accessing Pointer Functions

• – pointerFunctions

Class Methods

hashTableWithOptions:

Returns a hash table with given pointer functions options.

+ (id)hashTableWithOptions:(NSPointerFunctionsOptions)options

Parameters

options

A bit field that specifies the options for the elements in the hash table. For possible values, see “Hash Table Options”.

Return Value

A hash table with given pointer functions options.

Availability

• Available in Mac OS X v10.5 and later.

Declared In

hashTableWithWeakObjects

Returns a new hash table for storing weak references to its contents.

+ (id)hashTableWithWeakObjects

Return Value

A new has table that uses the options NSHashTableZeroingWeakMemory and NSPointerFunctionsObjectPersonality and has an initial capacity of 0.

Availability

• Available in Mac OS X v10.5 and later.

Declared In

Instance Methods

addObject:

Adds a given object to the receiver.

- (void)addObject:(id)object

Parameters

object

The object to add to the receiver.

Availability

• Available in Mac OS X v10.5 and later.

Declared In

allObjects

Returns an array that contains the receiver’s members.

- (NSArray *)allObjects

Return Value

An array that contains the receiver’s members.

Availability

• Available in Mac OS X v10.5 and later.

Declared In

anyObject

Returns one of the objects in the receiver.

- (id)anyObject

Return Value

One of the objects in the receiver, or nil if the receiver contains no objects.

Discussion

The object returned is chosen at the receiver’s convenience—the selection is not guaranteed to be random.

Availability

• Available in Mac OS X v10.5 and later.

Declared In

containsObject:

Returns a Boolean value that indicates whether the receiver contains a given object.

- (BOOL)containsObject:(id)anObject

Parameters

anObject

The object to test for membership in the receiver.

Return Value

YES if the receiver contains anObject, otherwise NO.

Availability

• Available in Mac OS X v10.5 and later.

Declared In

count

Returns the number of elements in the receiver.

- (NSUInteger)count

Return Value

The number of elements in the receiver.

Availability

• Available in Mac OS X v10.5 and later.

Declared In

initWithOptions:capacity:

Returns a hash table initialized with the given attributes.

- (id)initWithOptions:(NSPointerFunctionsOptions)options capacity:(NSUInteger)capacity

Parameters

options

A bit field that specifies the options for the elements in the hash table. For possible values, see “Hash Table Options”.

capacity

The initial number of elements the receiver can hold.

Return Value

A hash table initialized with options specified by options and initial capacity of capacity.

Availability

• Available in Mac OS X v10.5 and later.

Declared In

initWithPointerFunctions:capacity:

Returns a hash table initialized with the given functions and capacity.

- (id)initWithPointerFunctions:(NSPointerFunctions *)functions capacity:(NSUInteger)initialCapacity

Parameters

functions

The pointer functions for the new hash table.

initialCapacity

The initial capacity of the hash table.

Return Value

A hash table initialized with the given functions and capacity.

Discussion

Hash tables allocate additional memory as needed, so initialCapacity simply establishes the object’s initial capacity.

Availability

• Available in Mac OS X v10.5 and later.

Declared In

intersectHashTable:

Returns a Boolean value that indicates whether at least one element in the receiver is also present in another given hash table.

- (void)intersectHashTable:(NSHashTable *)other

Parameters

other

The hash table with which to compare the receiver.

Availability

• Available in Mac OS X v10.5 and later.

Declared In

intersectsHashTable:

Returns a Boolean value that indicates whether a given hash table intersects with the receiver.

- (BOOL)intersectsHashTable:(NSHashTable *)other

Parameters

other

The hash table with which to compare the receiver.

Return Value

YES if other intersects with the receiver, otherwise NO.

Availability

• Available in Mac OS X v10.5 and later.

Declared In

isEqualToHashTable:

Returns a Boolean value that indicates whether a given hash table is equal to the receiver.

- (BOOL)isEqualToHashTable:(NSHashTable *)other

Parameters

other

The hash table with which to compare the receiver.

Return Value

YES if the contents of other are equal to the contents of the receiver, otherwise NO.

Discussion

Two hash tables have equal contents if they each have the same number of members and if each member of one hash table is present in the other.

Availability

• Available in Mac OS X v10.5 and later.

Declared In

isSubsetOfHashTable:

Returns a Boolean value that indicates whether every element in the receiver is also present in another given hash table.

- (BOOL)isSubsetOfHashTable:(NSHashTable *)other

Parameters

other

The hash table with which to compare the receiver.

Return Value

YES if every element in the receiver is also present in other, otherwise NO.

Availability

• Available in Mac OS X v10.5 and later.

Declared In

member:

Determines whether a given object is an element in the receiver.

- (id)member:(id)object

Parameters

object

The object to test for membership in the receiver.

Return Value

If object is a member of the receiver, returns object, otherwise returns nil.

Availability

• Available in Mac OS X v10.5 and later.

Declared In

minusHashTable:

Removes from the receiver each element contained in another given hash table that is present in the receiver.

- (void)minusHashTable:(NSHashTable *)other

Parameters

other

The hash table of elements to remove from the receiver.

Discussion

If any element of other isn’t present in the receiver, this method has no effect on either the receiver or other.

Availability

• Available in Mac OS X v10.5 and later.

Declared In

objectEnumerator

Returns an enumerator object that lets you access each object in the receiver.

- (NSEnumerator *)objectEnumerator

Return Value

An enumerator object that lets you access each object in the receiver.

Discussion

The following code fragment illustrates how you can use this method.

NSEnumerator *enumerator = [myHashTable objectEnumerator];

id value;

while ((value = [enumerator nextObject])) {

    /* code that acts on the hash table's values */

}

Note that NSHashTable also supports the NSFastEnumeration protocol.

Availability

• Available in Mac OS X v10.5 and later.

Declared In

pointerFunctions

Returns the pointer functions for the receiver.

- (NSPointerFunctions *)pointerFunctions

Return Value

The pointer functions for the receiver.

Availability

• Available in Mac OS X v10.5 and later.

Declared In

removeAllObjects

Removes all objects from the receiver.

- (void)removeAllObjects

Availability

• Available in Mac OS X v10.5 and later.

Declared In

removeObject:

Removes a given object from the receiver.

- (void)removeObject:(id)object

Parameters

object

The object to remove from the receiver.

Availability

• Available in Mac OS X v10.5 and later.

Declared In

setRepresentation

Returns a set that contains the receiver’s members.

- (NSSet *)setRepresentation

Return Value

A set that contains the receiver’s members.

Availability

• Available in Mac OS X v10.5 and later.

Declared In

unionHashTable:

Adds to the receiver each element contained in another given hash table that is not already a member.

- (void)unionHashTable:(NSHashTable *)other

Parameters

other

The hash table of elements to add to the receiver.

Availability

• Available in Mac OS X v10.5 and later.

Declared In

Constants

NSHashTableOptions

Type to specify a bit-field used to define the behavior of elements in an NSHashTable object.

typedef NSUInteger NSHashTableOptions;

Discussion

For possible values, see “Hash Table Options.”

Availability

• Available in Mac OS X v10.5 and later.

Declared In

Hash Table Options

Components in a bit-field to specify the behavior of elements in an NSHashTable object.

enum {
   NSHashTableStrongMemory             = 0,
   NSHashTableZeroingWeakMemory        = NSPointerFunctionsZeroingWeakMemory,
   NSHashTableCopyIn                   = NSPointerFunctionsCopyIn,
   NSHashTableObjectPointerPersonality = NSPointerFunctionsObjectPointerPersonality,
};

Constants

NSHashTableStrongMemory

Equal to NSPointerFunctionsStrongMemory.

Available in Mac OS X v10.5 and later.

Declared in NSHashTable.h.

NSHashTableZeroingWeakMemory

Equal to NSPointerFunctionsZeroingWeakMemory.

Available in Mac OS X v10.5 and later.

Declared in NSHashTable.h.

NSHashTableCopyIn

Equal to NSPointerFunctionsCopyIn.

Available in Mac OS X v10.5 and later.

Declared in NSHashTable.h.

NSHashTableObjectPointerPersonality

Equal to NSPointerFunctionsObjectPointerPersonality.

Available in Mac OS X v10.5 and later.

Declared in NSHashTable.h.

Declared In

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