构建一个线程安全的字典
线程安全锁字典ConcurrentDictionary（并发字典）
ConcurrentDictionary的写操作比使用锁的字典Dictionary要慢得多，而读操作要快一些。因此如果对字典需要大量的线程安全的读操作，ConcurrentDictionary性能比较好。
使用单线程时，并发字典ConcurrentDictionary性能不及Dictionary，但是扩展到5到6个线程，并发字典性能会更好。
如果自己设计 则要+队列+同步 这样才能保证线程安全。。
/**
线程安全的字典
/**
线程安全的字典
*/
@interface OSSSyncMutableDictionary : NSObject
@property (nonatomic, strong) NSMutableDictionary *dictionary;
@property (nonatomic, strong) dispatch_queue_t dispatchQueue;
- (id)objectForKey:(id)aKey;
- (NSArray *)allKeys;
- (void)setObject:(id)anObject forKey:(id <NSCopying>)aKey;
- (void)removeObjectForKey:(id)aKey;
@end
@implementation OSSSyncMutableDictionary
- (instancetype)init {
if (self = [super init]) {
_dictionary = [NSMutableDictionary new];
_dispatchQueue = dispatch_queue_create("com.aliyun.aliyunsycmutabledictionary", DISPATCH_QUEUE_SERIAL);
}
return self;
}
- (NSArray *)allKeys {
__block NSArray *allKeys = nil;
dispatch_sync(self.dispatchQueue, ^{
allKeys = [self.dictionary allKeys];
});
return allKeys;
}
- (id)objectForKey:(id)aKey {
__block id returnObject = nil;
dispatch_sync(self.dispatchQueue, ^{
returnObject = [self.dictionary objectForKey:aKey];
});
return returnObject;
}
- (void)setObject:(id)anObject forKey:(id <NSCopying>)aKey {
dispatch_sync(self.dispatchQueue, ^{
[self.dictionary setObject:anObject forKey:aKey];
});
}
- (void)removeObjectForKey:(id)aKey {
dispatch_sync(self.dispatchQueue, ^{
[self.dictionary removeObjectForKey:aKey];
});
}
@end
