libObjCAttr/Attribute/RFAttributeCacheManager.m

//
//  RFAttributeCacheManager.m
//  libObjCAttr
//
//  Copyright (c) 2014 EPAM Systems, Inc. All rights reserved.
//
//  Redistribution and use in source and binary forms, with or without
//  modification, are permitted provided that the following conditions are met:
//
//  Redistributions of source code must retain the above copyright notice, this
//  list of conditions and the following disclaimer.
//  Redistributions in binary form must reproduce the above copyright notice, this
//  list of conditions and the following disclaimer in the documentation and/or
//  other materials provided with the distribution.
//  Neither the name of the EPAM Systems, Inc.  nor the names of its contributors
//  may be used to endorse or promote products derived from this software without
//  specific prior written permission.
//
//  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
//  ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
//  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
//  DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
//  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
//  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
//  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
//  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
//  OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
//  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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//  See the NOTICE file and the LICENSE file distributed with this work
//  for additional information regarding copyright ownership and licensing


#import "RFAttributeCacheManager.h"

#ifndef TARGET_OS_MAC
  #import <UIKit/UIKit.h>
#endif


@interface RFAttributeCacheManager ()

@end



@implementation RFAttributeCacheManager {
    NSMutableDictionary * _sharedCache;
    /**
     The queue to work on. http://stackoverflow.com/questions/12511976/app-crashes-after-xcode-upgrade-to-4-5-assigning-retained-object-to-unsafe-unre
     */
#if OS_OBJECT_USE_OBJC
    dispatch_queue_t _queue; // this is for Xcode 4.5 with LLVM 4.1 and iOS 6 SDK
#else
    dispatch_queue_t _queue; // this is for older Xcodes with older SDKs
#endif
}


#pragma mark - Public interface

+ (id)objectForKey:(id<NSCopying> )key {
    RFAttributeCacheManager *cacheManager = [self attributeCacheManager];
    __block id object;
    dispatch_sync(cacheManager->_queue, ^{
        object = cacheManager->_sharedCache[key];
    });

    return object;
}

+ (void)setObject:(id)object forKey:(id<NSCopying>)key {
    RFAttributeCacheManager *cacheManager = [self attributeCacheManager];
    dispatch_sync(cacheManager->_queue, ^{
        cacheManager->_sharedCache[key] = object;
    });
}


#pragma mark - Private Lifecycle

+ (instancetype)attributeCacheManager {
    static dispatch_once_t onceToken;
    static id sharedCacheManager = nil;
    dispatch_once(&onceToken, ^{
        sharedCacheManager = [[self alloc] init];
    });
    
    return sharedCacheManager;
}

- (id)init {
    self = [super init];
    if (self) {
        _queue = dispatch_queue_create(NULL, DISPATCH_QUEUE_SERIAL);
        _sharedCache = [[NSMutableDictionary alloc] init];
#ifndef TARGET_OS_MAC
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(didRecieveMemoryWarning) name:UIApplicationDidReceiveMemoryWarningNotification object:nil];
#endif
    }
    return self;
}

- (NSMutableDictionary *)sharedCache {
    __block id cache;
    dispatch_sync(_queue, ^{
        cache = self->_sharedCache;
    });
    
    return cache;
}

#ifndef TARGET_OS_MAC
- (void)didRecieveMemoryWarning {
    dispatch_sync(_queue, ^{
        [self->_sharedCache removeAllObjects];
    });
}
#endif

@end