Multi-thread daata access issue, @synchronized & serial queue

Question

As you may have experienced, access none-thread safe variables is a big headache. For iOS one simple solution is to use keyword @synchronized, which will add NSLock to insure the data can be accessed by unique one thread, the disadvantage is as below:

1. Lock too many will reduce app performance greatly, especially when invoked by main thread.

2. Dead lock will occur when logic becomes complex.

Based on the above considerations, we prefer to use serial queue to handle, each thread safe critical operation will append to the end of the queue, it is a great solution, but the problem is that all access interfaces should by designed in asyn style, see the following one.

-(id)objectForKey:(NSString *)key;

The people who invoke this class aren't reluctant to design in this way. Anyone who has experience on this field please share and discuss together.

Answer 1

The final solution is using NSUserDefault to store small data, for large cache data put them in file maintained by ourselves.

Per Apple doc the advantage of NSUserDefault is thread safe and will do synchronize work periodically.