# CFDictionary ``` class CFDictionary ``` ## Overview CFDictionary and its derived mutable type, [`CFMutableDictionary`](/documentation/CoreFoundation/CFMutableDictionary), manage associations of key-value pairs. CFDictionary creates static dictionaries where you set the key-value pairs when first creating a dictionary and cannot modify them afterward; CFMutableDictionary creates dynamic dictionaries where you can add or delete key-value pairs at any time, and the dictionary automatically allocates memory as needed. A key-value pair within a dictionary is called an entry. Each entry consists of one object that represents the key and a second object that is that key’s value. Within a dictionary, the keys are unique. That is, no two keys in a single dictionary are equal (as determined by the equal callback). Internally, a dictionary uses a hash table to organize its storage and to provide rapid access to a value given the corresponding key. Keys for a CFDictionary may be of any C type, however note that if you want to convert a CFPropertyList to XML, any dictionary’s keys must be CFString objects. You create static dictionaries using either the [`CFDictionaryCreate(_:_:_:_:_:_:)`](/documentation/CoreFoundation/CFDictionaryCreate(_:_:_:_:_:_:)) or [`CFDictionaryCreateCopy(_:_:)`](/documentation/CoreFoundation/CFDictionaryCreateCopy(_:_:)) function. Key-value pairs are passed as parameters to [`CFDictionaryCreate(_:_:_:_:_:_:)`](/documentation/CoreFoundation/CFDictionaryCreate(_:_:_:_:_:_:)). When adding key-value pairs to a dictionary, the keys and values are not copied—they are retained so they are not invalidated before the dictionary is deallocated. CFDictionary provides functions for querying the values of a dictionary. The function [`CFDictionaryGetCount(_:)`](/documentation/CoreFoundation/CFDictionaryGetCount(_:)) returns the number of key-value pairs in a dictionary; the [`CFDictionaryContainsValue(_:_:)`](/documentation/CoreFoundation/CFDictionaryContainsValue(_:_:)) function checks if a value is in a dictionary; and [`CFDictionaryGetKeysAndValues(_:_:_:)`](/documentation/CoreFoundation/CFDictionaryGetKeysAndValues(_:_:_:)) returns a C array containing all the values and a C array containing all the keys in a dictionary. The [`CFDictionaryApplyFunction(_:_:_:)`](/documentation/CoreFoundation/CFDictionaryApplyFunction(_:_:_:)) function lets you apply a function to all key-value pairs in a dictionary. CFDictionary is “toll-free bridged” with its Cocoa Foundation counterpart, . This means that the Core Foundation type is interchangeable in function or method calls with the bridged Foundation object. Therefore, in a method where you see an `NSDictionary *` parameter, you can pass in a `CFDictionaryRef`, and in a function where you see a `CFDictionaryRef` parameter, you can pass in an NSDictionary instance. This also applies to concrete subclasses of NSDictionary. See [Toll-Free Bridged Types](https://developer.apple.com/library/archive/documentation/CoreFoundation/Conceptual/CFDesignConcepts/Articles/tollFreeBridgedTypes.html#//apple_ref/doc/uid/TP40010677) for more information on toll-free bridging. ## Topics ### Creating a dictionary [`CFDictionaryCreate(_:_:_:_:_:_:)`](/documentation/CoreFoundation/CFDictionaryCreate(_:_:_:_:_:_:)) Creates an immutable dictionary containing the specified key-value pairs. [`CFDictionaryCreateCopy(_:_:)`](/documentation/CoreFoundation/CFDictionaryCreateCopy(_:_:)) Creates and returns a new immutable dictionary with the key-value pairs of another dictionary. ### Examining a dictionary [`CFDictionaryContainsKey(_:_:)`](/documentation/CoreFoundation/CFDictionaryContainsKey(_:_:)) Returns a Boolean value that indicates whether a given key is in a dictionary. [`CFDictionaryContainsValue(_:_:)`](/documentation/CoreFoundation/CFDictionaryContainsValue(_:_:)) Returns a Boolean value that indicates whether a given value is in a dictionary. [`CFDictionaryGetCount(_:)`](/documentation/CoreFoundation/CFDictionaryGetCount(_:)) Returns the number of key-value pairs in a dictionary. [`CFDictionaryGetCountOfKey(_:_:)`](/documentation/CoreFoundation/CFDictionaryGetCountOfKey(_:_:)) Returns the number of times a key occurs in a dictionary. [`CFDictionaryGetCountOfValue(_:_:)`](/documentation/CoreFoundation/CFDictionaryGetCountOfValue(_:_:)) Counts the number of times a given value occurs in the dictionary. [`CFDictionaryGetKeysAndValues(_:_:_:)`](/documentation/CoreFoundation/CFDictionaryGetKeysAndValues(_:_:_:)) Fills two buffers with the keys and values from a dictionary. [`CFDictionaryGetValue(_:_:)`](/documentation/CoreFoundation/CFDictionaryGetValue(_:_:)) Returns the value associated with a given key. [`CFDictionaryGetValueIfPresent(_:_:_:)`](/documentation/CoreFoundation/CFDictionaryGetValueIfPresent(_:_:_:)) Returns a Boolean value that indicates whether a given value for a given key is in a dictionary, and returns that value indirectly if it exists. ### Applying a function to a dictionary [`CFDictionaryApplyFunction(_:_:_:)`](/documentation/CoreFoundation/CFDictionaryApplyFunction(_:_:_:)) Calls a function once for each key-value pair in a dictionary. ### Getting the CFDictionary type ID [`CFDictionaryGetTypeID()`](/documentation/CoreFoundation/CFDictionaryGetTypeID()) Returns the type identifier for the CFDictionary opaque type. ### Callbacks [`CFDictionaryApplierFunction`](/documentation/CoreFoundation/CFDictionaryApplierFunction) Prototype of a callback function that may be applied to every key-value pair in a dictionary. [`CFDictionaryCopyDescriptionCallBack`](/documentation/CoreFoundation/CFDictionaryCopyDescriptionCallBack) Prototype of a callback function used to get a description of a value or key in a dictionary. [`CFDictionaryEqualCallBack`](/documentation/CoreFoundation/CFDictionaryEqualCallBack) Prototype of a callback function used to determine if two values or keys in a dictionary are equal. [`CFDictionaryHashCallBack`](/documentation/CoreFoundation/CFDictionaryHashCallBack) Prototype of a callback function invoked to compute a hash code for a key. Hash codes are used when key-value pairs are accessed, added, or removed from a collection. [`CFDictionaryReleaseCallBack`](/documentation/CoreFoundation/CFDictionaryReleaseCallBack) Prototype of a callback function used to release a key-value pair before it’s removed from a dictionary. [`CFDictionaryRetainCallBack`](/documentation/CoreFoundation/CFDictionaryRetainCallBack) Prototype of a callback function used to retain a value or key being added to a dictionary. ### Data Types [`CFDictionaryKeyCallBacks`](/documentation/CoreFoundation/CFDictionaryKeyCallBacks) This structure contains the callbacks used to retain, release, describe, and compare the keys in a dictionary. [`CFDictionaryValueCallBacks`](/documentation/CoreFoundation/CFDictionaryValueCallBacks) This structure contains the callbacks used to retain, release, describe, and compare the values in a dictionary. ### Constants [Predefined Callback Structures](/documentation/CoreFoundation/cfdictionary-predefined-callback-structures) CFDictionary provides some predefined callbacks for your convenience. ## See Also [Property List Programming Topics for Core Foundation](https://developer.apple.com/library/archive/documentation/CoreFoundation/Conceptual/CFPropertyLists/CFPropertyLists.html#//apple_ref/doc/uid/10000130i) [Collections Programming Topics for Core Foundation](https://developer.apple.com/library/archive/documentation/CoreFoundation/Conceptual/CFCollections/CFCollections.html#//apple_ref/doc/uid/10000124i) --- Copyright © 2026 Apple Inc. 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