Next Page >

Hide TOC

NSPointerFunctions Class Reference

Inherits from	NSObject
Conforms to	NSCopying NSObject (NSObject)
Framework	/System/Library/Frameworks/Foundation.framework
Availability	Available in Mac OS X v10.5 and later.
Declared in	NSPointerFunctions.h
Companion guides	Collections Programming Topics for Cocoa Garbage Collection Programming Guide

Overview

An instance of NSPointerFunctions defines callout functions appropriate for managing a pointer reference held somewhere else.

The functions specified by an instance of NSPointerFunctions are separated into two clusters—those that define “personality” such as “object” or "C-string”, and those that describe memory management issues such as a memory deallocation function. There are constants for common personalities and memory manager selections (see “Memory and Personality Options”).

NSHashTable, NSMapTable, and NSPointerArray use an NSPointerFunctions object to define the acquisition and retention behavior for the pointers they manage. Note, however, that not all combinations of personality and memory management behavior are valid for these collections. The pointer collection objects copy the NSPointerFunctions object on input and output, so you cannot usefully subclass NSPointerFunctions.

Tasks

Creating and Initializing an NSPointerFunctions Object

Personality Functions

Memory Configuration

Properties

For more about Objective-C properties, see “Properties” in The Objective-C 2.0 Programming Language.

acquireFunction

The function used to acquire memory.

@property void *(*acquireFunction)(const void *src, NSUInteger (*size)(const void *item), BOOL shouldCopy)

Discussion

This specifies the function to use for copy-in operations.

Availability

Available in Mac OS X v10.5 and later.

Declared In

NSPointerFunctions.h

descriptionFunction

The function used to describe elements.

@property NSString *(*descriptionFunction)(const void *item)

Discussion

This function is used by description methods for hash and map tables.

Availability

Available in Mac OS X v10.5 and later.

Declared In

NSPointerFunctions.h

hashFunction

The hash function.

@property NSUInteger (*hashFunction)(const void *item, NSUInteger (*size)(const void *item))

Availability

Available in Mac OS X v10.5 and later.

Declared In

NSPointerFunctions.h

isEqualFunction

The function used to compare pointers.

@property BOOL (*isEqualFunction)(const void *item1, const void*item2, NSUInteger (*size)(const void *item))

Availability

Available in Mac OS X v10.5 and later.

Declared In

NSPointerFunctions.h

relinquishFunction

The function used to relinquish memory.

@property void (*relinquishFunction)(const void *item, NSUInteger (*size)(const void *item))

Discussion

This specifies the function to use when an item is removed from a table or pointer array.

Availability

Available in Mac OS X v10.5 and later.

Declared In

NSPointerFunctions.h

sizeFunction

The function used to determine the size of pointers.

@property NSUInteger (*sizeFunction)(const void *item)

Discussion

This function is used for copy-in operations (unless the collection has an object personality).

Availability

Available in Mac OS X v10.5 and later.

Declared In

NSPointerFunctions.h

usesStrongWriteBarrier

Specifies whether, in a garbage collected environment, pointers should be assigned using a strong write barrier.

@property BOOL usesStrongWriteBarrier

Discussion

If you use garbage collection, read and write barrier functions must be used when pointers are from memory scanned by the collector.

Availability

Available in Mac OS X v10.5 and later.

Declared In

NSPointerFunctions.h

usesWeakReadAndWriteBarriers

Specifies whether, in a garbage collected environment, pointers should use weak read and write barriers.

@property BOOL usesWeakReadAndWriteBarriers

Discussion

If you use garbage collection, read and write barrier functions must be used when pointers are from memory scanned by the collector.

Availability

Available in Mac OS X v10.5 and later.

Declared In

NSPointerFunctions.h

Class Methods

pointerFunctionsWithOptions:

Returns a new NSPointerFunctions object initialized with the given options.

+ (id)pointerFunctionsWithOptions:(NSPointerFunctionsOptions)options

Parameters

options: The options for the new NSPointerFunctions object.

Return Value

A new NSPointerFunctions object initialized with the given options.

Availability

Available in Mac OS X v10.5 and later.

Declared In

NSPointerFunctions.h

Instance Methods

initWithOptions:

Returns an NSPointerFunctions object initialized with the given options.

- (id)initWithOptions:(NSPointerFunctionsOptions)options

Parameters

options: The options for the new NSPointerFunctions object.

Return Value

The receiver, initialized with the given options.

Availability

Available in Mac OS X v10.5 and later.

Declared In

NSPointerFunctions.h

Constants

NSPointerFunctionsOptions

Defines the memory and personality options for an NSPointerFunctions object.

typedef NSUInteger NSPointerFunctionsOptions;

Discussion

For values, see “Memory and Personality Options.”

Availability

Available in Mac OS X v10.5 and later.

Declared In

NSPointerFunctions.h

Memory and Personality Options

Specify memory and personality options for an NSPointerFunctions object.

enum {
   NSPointerFunctionsStrongMemory = (0 << 0),
   NSPointerFunctionsZeroingWeakMemory = (1 << 0),
   NSPointerFunctionsOpaqueMemory = (2 << 0),
   NSPointerFunctionsMallocMemory = (3 << 0),
   NSPointerFunctionsMachVirtualMemory = (4 << 0),
   NSPointerFunctionsObjectPersonality = (0 << 8),
   NSPointerFunctionsOpaquePersonality = (1 << 8),
   NSPointerFunctionsObjectPointerPersonality = (2 << 8),
   NSPointerFunctionsCStringPersonality = (3 << 8),
   NSPointerFunctionsStructPersonality = (4 << 8),
   NSPointerFunctionsIntegerPersonality = (5 << 8),
   NSPointerFunctionsCopyIn = (1 << 16),
};

Constants

NSPointerFunctionsStrongMemory

Use strong write-barriers to backing store; use garbage-collected memory on copy-in.

This is the default memory value.

As a special case, if you do not use garbage collection and specify this value in conjunction with NSPointerFunctionsObjectPersonality then the NSPointerFunctions object uses retain and release.

Available in Mac OS X v10.5 and later.