NSString保存到本地，读取

保存到本地：

 NSError *error = NULL;        BOOL success = [str writeToFile:document_cache_forum_top atomically:YES encoding:NSUTF8StringEncoding error:&error];        if(!success)        {            NSLog( @"error saving to %@ - %@", document_cache_forum_top, [error localizedDescription] );        }

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读取str：

NSError *error = NULL;        NSString *str = [NSString stringWithContentsOfFile:document_cache_forum_top encoding:NSUTF8StringEncoding error:&error];        

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