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DFCache provides composite in-memory and on-disk cache with LRU cleanup. It is implemented as a set of reusable classes and protocols with concise and extensible API.

DFCache is not intended to be used as a NSURLCache alternative. If you use Foundation URL loading system you should use NSURLCache that supports HTTP Caching.

Features

  • LRU cleanup (discards least recently used items first)
  • Metadata implemented on top on UNIX extended file attributes
  • Builtin support for objects conforming to <NSCoding> protocol. Can be easily extended to support more protocols and classes
  • First class UIImage support including background image decompression
  • Batch methods to retrieve cached entries
  • Thoroughly tested and well-documented

Requirements

iOS 6.0+ / watchOS 2.0+ / OS X 10.8+ / tvOS 9.0+

Usage

DFCache

Store, retrieve and remove object

DFCache *cache = [[DFCache alloc] initWithName:@"image_cache"];
NSString *key = @"http://..."; // Key can by any arbitrary string.
UIImage *image = ...; // Instead of UIImage you can use the same API for objects conforming to NSCoding protocol

// Store image
[cache storeObject:image forKey:key];
// [cache storeObject:image forKey:key data:data]; - you can store original image data

// Retrieve decompressed image
[cache cachedObjectForKey:key completion:^(id object) {
    // All disk IO operations are run on serial dispatch queue
    // which guarantees that the object is retrieved successfully.
    NSLog(@"Did retrieve cached object %@", object);
}];

[cache removeObjectForKey:key];

Set and read metadata

DFCache *cache = [[DFCache alloc] initWithName:@"sample_cache"];
NSDictionary *object = @{ @"key" : @"value" };
[cache storeObject:object forKey:@"key"];
[cache setMetadata:@{ @"revalidation_date" : [NSDate date] } forKey:@"key"];
NSDictionary *metadata = [cache metadataForKey:@"key"];

DFCache (DFCacheExtended)

Retrieve batch of objects

DFCache *cache = ...;
[cache batchCachedObjectsForKeys:keys completion:^(NSDictionary *batch) {
    for (NSString *key in keys) {
        id object = batch[key];
        // Do something with an object.
    }
}];

DFFileStorage

Write and read data

DFFileStorage *storage = [[DFFileStorage alloc] initWithPath:path error:nil];
[storage setData:data forKey:@"key"];
[storage dataForKey:@"key"];

Enumerate contents

DFFileStorage *storage = [[DFFileStorage alloc] initWithPath:path error:nil];
NSArray *resourceKeys = @[ NSURLContentModificationDateKey, NSURLFileAllocatedSizeKey ];
NSArray *contents = [storage contentsWithResourceKeys:resourceKeys];
for (NSURL *fileURL in contents) {
    // Use file URL and pre-fetched file attributes.
}

NSURL (DFExtendedFileAttributes)

Set and read extended file attributes

NSURL *fileURL = [NSURL fileURLWithPath:path];
[fileURL df_setExtendedAttributeValue:@"value" forKey:@"attr_key"];
NSString *value = [fileURL df_extendedAttributeValueForKey:@"attr_key" error:NULL];
[fileURL df_removeExtendedAttributeForKey];

Design

Class Description
DFCache Asynchronous composite in-memory and on-disk cache with LRU cleanup. Uses NSCache for in-memory caching and DFDiskCache for on-disk caching. Provides API for associating metadata with cache entries.
<DFValueTransforming> Protocol for describing a way of encoding and decoding objects.
<DFValueTransformerFactory> Protocol for matching objects with value transformers.
DFFileStorage Key-value file storage.
DFDiskCache Disk cache extends file storage functionality by providing LRU (least recently used) cleanup.
NSURL (DFExtendedFileAttributes) Objective-c wrapper of UNIX extended file attributes. Extended attributes extend the basic attributes associated with files and directories in the file system. They are stored as name:data pairs associated with file system objects (files, directories, symlinks, etc). See setxattr(2).
DFCache (DFCacheExtended) Set of methods that extend DFCache functionality by allowing you to retrieve cached entries in batches.

NSCache on iOS 7.0

NSCache auto-removal policies have change with the release of iOS 7.0. Make sure that you use reasonable total cost limit or count limit. Or else NSCache won't be able to evict memory properly. Typically, the obvious cost is the size of the object in bytes. Keep in mind that DFCache automatically removes all object from memory cache on memory warning for you.

Installation

CocoaPods

To install DFCache add a dependency to your Podfile:

# source 'https://github.com/CocoaPods/Specs.git'
# use_frameworks!
# platform :ios, "6.0" / :watchos, "2.0" / :osx, "10.8" / :tvos, "9.0"

pod "DFCache"

Carthage

To install DFCache add a dependency to your Cartfile:

github "kean/DFCache"

Contacts

License

DFCache is available under the MIT license. See the LICENSE file for more info.

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Composite LRU cache with fast metadata using UNIX extended file attributes

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