CFBag

Overview

CFBag and its derived mutable type, CFMutableBag, manage non-sequential collections of values called bags in which there can be duplicate values. CFBag creates static bags and CFMutableBag creates dynamic bags.

Use bags or sets as an alternative to arrays when the order of elements isn't important and performance in testing whether a value is contained in the collection is a consideration—while arrays are ordered, testing for membership is slower than with bags or sets. Use bags over sets if you want to allow duplicate values in your collections.

You create a static bag object using either the CFBagCreate(_:_:_:_:) or CFBagCreateCopy(_:_:) function. These functions return a bag containing the values you pass in as arguments. (Note that bags can't contain NULL pointers; in most cases, though, you can use the kCFNull constant instead.) Values are not copied but retained using the retain callback provided when the bag was created. Similarly, when a value is removed from a bag, it is released using the release callback.

CFBag provides functions for querying the values of a bag. The CFBagGetCount(_:) returns the number of values in a bag, the CFBagContainsValue(_:_:) function checks if a value is in a bag, and CFBagGetValues(_:_:) returns a C array containing all the values in a bag.

The CFBagApplyFunction(_:_:_:) function lets you apply a function to all values in a bag.

Symbols

Creating a Bag

func CFBagCreateCopy(CFAllocator!, CFBag!)

Creates an immutable bag with the values of another bag.

Examining a Bag

func CFBagContainsValue(CFBag!, UnsafeRawPointer!)

Reports whether or not a value is in a bag.

func CFBagGetCount(CFBag!)

Returns the number of values currently in a bag.

func CFBagGetCountOfValue(CFBag!, UnsafeRawPointer!)

Returns the number of times a value occurs in a bag.

func CFBagGetValue(CFBag!, UnsafeRawPointer!)

Returns a requested value from a bag.

func CFBagGetValueIfPresent(CFBag!, UnsafeRawPointer!, UnsafeMutablePointer<UnsafeRawPointer?>!)

Reports whether or not a value is in a bag, and returns that value indirectly if it exists.

Applying a Function to the Contents of a Bag

Getting the CFBag Type ID

func CFBagGetTypeID()

Returns the type identifier for the CFBag opaque type.

Callbacks

CFBagApplierFunction

Prototype of a callback function that may be applied to every value in a bag.

CFBagCopyDescriptionCallBack

Prototype of a callback function used to get a description of a value in a bag.

CFBagEqualCallBack

Prototype of a callback function used to determine if two values in a bag are equal.

CFBagHashCallBack

Prototype of a callback function invoked to compute a hash code for a value. Hash codes are used when values are accessed, added, or removed from a collection.

CFBagReleaseCallBack

Prototype of a callback function used to release a value before it’s removed from a bag.

CFBagRetainCallBack

Prototype of a callback function used to retain a value being added to a bag.

Data Types

CFBagCallBacks

This structure contains the callbacks used to retain, release, describe, and compare the values of a CFBag object.

CFBag

A reference to an immutable bag object.

Constants

Predefined Callback Structures

CFBag provides some predefined callbacks for your convenience.