NIMemoryCache Class Reference

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Overview

An in-memory cache for storing objects with expiration support.

The Nimbus in-memory object cache allows you to store objects in memory with an expiration date attached. Objects with expiration dates drop out of the cache when they have expired.

Definition at line 38 of file NIInMemoryCache.h.

Inheritance diagram for NIMemoryCache:

Methods
Creating an In-Memory Cache
(id)	- initWithCapacity:
Querying an In-Memory Cache
(NSUInteger)	- count
Storing Objects in the Cache
(void)	- storeObject:withName:
(void)	- storeObject:withName:expiresAfter:
Removing Objects from the Cache
(void)	- removeObjectWithName:
(void)	- removeAllObjects
Accessing Objects in the Cache
(id)	- objectWithName:
(BOOL)	- containsObjectWithName:
(NSDate *)	- dateOfLastAccessWithName:
(NSString *)	- nameOfLeastRecentlyUsedObject
(NSString *)	- nameOfMostRecentlyUsedObject
Reducing Memory Usage Explicitly
(void)	- reduceMemoryUsage
Subclassing
The following methods are provided to aid in subclassing and are not meant to be used externally.
(BOOL)	- willSetObject:withName:previousObject:
(void)	- didSetObject:withName:
(void)	- willRemoveObject:withName:

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Method Documentation

- (id) initWithCapacity:

(NSUInteger)

capacity

Initializes a newly allocated cache with the given capacity.

Returns:

An in-memory cache initialized with the given capacity.

Definition at line 109 of file NIInMemoryCache.m.

- (NSUInteger) count

Returns the number of objects currently in the cache.

Returns:

The number of objects currently in the cache.

Definition at line 358 of file NIInMemoryCache.m.

- (void) storeObject:		(id)	object
withName:		(NSString *)	name

Stores an object in the cache.

The object will be stored without an expiration date. The object will stay in the cache until it's bumped out due to the cache's memory limit.

Parameters:

object	The object being stored in the cache.
name	The name used as a key to store this object.

Definition at line 215 of file NIInMemoryCache.m.

- (void) storeObject:		(id)	object
withName:		(NSString *)	name
expiresAfter:		(NSDate *)	expirationDate

Stores an object in the cache with an expiration date.

If an object is stored with an expiration date that has already passed then the object will not be stored in the cache and any existing object will be removed. The rationale behind this is that the object would be removed from the cache the next time it was accessed anyway.

Parameters:

object	The object being stored in the cache.
name	The name used as a key to store this object.
expirationDate	A date after which this object is no longer valid in the cache.

Definition at line 221 of file NIInMemoryCache.m.

- (void) removeObjectWithName:

(NSString *)

name

Removes an object from the cache.

Parameters:

name	The name used as a key to store this object.

Definition at line 328 of file NIInMemoryCache.m.

- (void) removeAllObjects

Removes all objects from the cache, regardless of expiration dates.

This will completely clear out the cache and all objects in the cache will be released.

Definition at line 334 of file NIInMemoryCache.m.

- (id) objectWithName:

(NSString *)

name

Retrieves an object from the cache.

If the object has expired then the object will be removed from the cache and nil will be returned.

Returns:

The object stored in the cache. The object is retained and autoreleased to ensure that it survives this run loop if you then remove it from the cache.

Definition at line 254 of file NIInMemoryCache.m.

- (BOOL) containsObjectWithName:

(NSString *)

name

Returns a Boolean value that indicates whether an object with the given name is present in the cache.

Does not update the access time of the object.

If the object has expired then the object will be removed from the cache and NO will be returned.

Returns:

YES if an object with the given name is present in the cache and has not expired, otherwise NO.

Definition at line 276 of file NIInMemoryCache.m.

- (NSDate *) dateOfLastAccessWithName:

(NSString *)

name

Returns the date that the object with the given name was last accessed.

Does not update the access time of the object.

If the object has expired then the object will be removed from the cache and nil will be returned.

Returns:

The last access date of the object if it exists and has not expired, nil otherwise.

Definition at line 289 of file NIInMemoryCache.m.

- (NSString *) nameOfLeastRecentlyUsedObject

Retrieve the name of the object that was least recently used.

This will not update the access time of the object.

If the cache is empty, returns nil.

Definition at line 302 of file NIInMemoryCache.m.

- (NSString *) nameOfMostRecentlyUsedObject

Retrieve the key with the most fresh access.

This will not update the access time of the object.

If the cache is empty, returns nil.

Definition at line 315 of file NIInMemoryCache.m.

- (void) reduceMemoryUsage

Removes all expired objects from the cache.

Subclasses may add additional functionality to this implementation. Subclasses should call super in order to prune expired objects.

This will be called when UIApplicationDidReceiveMemoryWarningNotification is posted.

Definition at line 341 of file NIInMemoryCache.m.

- (BOOL) willSetObject:		(id)	object
withName:		(NSString *)	name
previousObject:		(id)	previousObject

An object is about to be stored in the cache.

Parameters:

object	The object that is about to be stored in the cache.
name	The cache name for the object.
previousObject	The object previously stored in the cache. This may be the same as object.

Returns:

YES If object is allowed to be stored in the cache.

Definition at line 190 of file NIInMemoryCache.m.

- (void) didSetObject:		(id)	object
withName:		(NSString *)	name

An object has been stored in the cache.

Parameters:

object	The object that was stored in the cache.
name	The cache name for the object.

Definition at line 197 of file NIInMemoryCache.m.

- (void) willRemoveObject:		(id)	object
withName:		(NSString *)	name

An object is about to be removed from the cache.

Parameters:

object	The object about to removed from the cache.
name	The cache name for the object about to be removed.

Definition at line 203 of file NIInMemoryCache.m.