MBThreadsafeCache Class Reference

Inherits from NSObject
Declared in MBThreadsafeCache.h

Overview

This class implements in-memory object cache that can be safely shared among multiple threads simultaneously.

The cache provides an accessor/mutator interface similar to NSDictionary and NSMutableDictionary, and supports keyed subscripting.

Note: Classes that wish to subclass MBThreadsafeCache should refer to the internal MBThreadsafeCache(ForSubclassEyesOnly) methods declared in the header file MBThreadsafeCache+Subclassing.h.

Other Methods

– initWithExceptionProtection:ignoreMemoryWarnings:

Initializes a new MBThreadsafeCache instance.

- (nonnull instancetype)initWithExceptionProtection:(BOOL)protect ignoreMemoryWarnings:(BOOL)ignore

Parameters

protect

If YES, the cache will ensure that internal exceptions do not leave locks in an inconsistent state. This adds overhead, and is generally not needed unless subclasses override primitive hooks that may throw exceptions.
ignore

If YES, the cache will not automatically clear itself when a memory warning occurs.

Declared In

MBThreadsafeCache.h

– initWithExceptionProtection:

Initializes a new MBThreadsafeCache instance.

- (nonnull instancetype)initWithExceptionProtection:(BOOL)protect

Parameters

protect

If YES, the cache will ensure that internal exceptions do not leave locks in an inconsistent state. This adds overhead, and is generally not needed unless subclasses override primitive hooks that may throw exceptions.

Declared In

MBThreadsafeCache.h

– init

The default initializer for MBThreadsafeCache instances.

- (nonnull instancetype)init

Discussion

Equivalent to calling initWithExceptionProtection:NO ignoreMemoryWarnings:NO.

Declared In

MBThreadsafeCache.h

Accessing cached items

– isKeyInCache:

Determines whether a given key has a corresponding value in the cache.

- (BOOL)isKeyInCache:(nonnull id)key

Parameters

key

The key.

Return Value

YES if there is a value for the given key in the cache; NO otherwise.

Declared In

MBThreadsafeCache.h

– objectForKey:

Retrieves a cached object value given its key.

- (nullable id)objectForKey:(nonnull id)key

Parameters

key

The key whose associated value is to be retrieved.

Return Value

The value associated with key. May be nil.

Declared In

MBThreadsafeCache.h

Modifying the cache

– setObject:forKey:

Sets a cached object value and associates it with the given key.

- (void)setObject:(nonnull id)obj forKey:(nonnull id)key

Parameters

obj

The new cached value.
key

The key whose associated value is to be set.

Declared In

MBThreadsafeCache.h

– removeObjectForKey:

Removes from the cache the object associated with the given key.

- (void)removeObjectForKey:(nonnull id)key

Parameters

key

The key whose associated value is to be removed.

Declared In

MBThreadsafeCache.h

Keyed subscripting support

– objectForKeyedSubscript:

Allows accessing a cached value using the Objective-C keyed subscripting notation.

- (nullable id)objectForKeyedSubscript:(nonnull id)key

Parameters

key

The key whose associated value is to be retrieved.

Return Value

The value associated with key. May be nil.

Declared In

MBThreadsafeCache.h

– setObject:forKeyedSubscript:

Allows setting a cached value using the Objective-C keyed subscripting notation.

- (void)setObject:(nonnull id)obj forKeyedSubscript:(nonnull id)key

Parameters

obj

The new cached value.
key

The key whose associated value is to be set.

Declared In

MBThreadsafeCache.h

Memory management

– clearMemoryCache

Empties the in-memory object cache.

- (void)clearMemoryCache

Discussion

Depending on how the cache instance was initialized, the memory cache may be cleared automatically in response to memory warnings.

Declared In

MBThreadsafeCache.h

– memoryWarning

This method is called automatically when a memory warning occurs, unless the cache was explicitly initialized to ignore memory warnings.

- (void)memoryWarning

Discussion

The default implementation simply calls clearMemoryCache; however, subclasses may override this to perform additional cleanup when a memory warning occurs.

Declared In

MBThreadsafeCache.h

Manipulating the cache lock

– lock

Locks the cache.

- (void)lock

Discussion

Used internally by the MBThreadsafeCache implementation and subclasses.

Note: You will generally not need to call this directly unless you want to make multiple changes to the cache atomically.

Declared In

MBThreadsafeCache.h

– unlock

Unlocks the cache.

- (void)unlock

Discussion

Used internally by the MBThreadsafeCache implementation and subclasses.

Note: You will generally not need to call this directly unless you want to make multiple changes to the cache atomically.

Declared In

MBThreadsafeCache.h