一段异步操作的代码（清理缓存）

dispatch_async(
dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)
, ^{
NSString *cachPath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) objectAtIndex:0];

NSArray *files = [[NSFileManager defaultManager] subpathsAtPath:cachPath];
NSLog(@"files :%d",[files count]);
for (NSString *p in files) {
NSError *error;
NSString *path = [cachPath stringByAppendingPathComponent:p];
if ([[NSFileManager defaultManager] fileExistsAtPath:path]) {
[[NSFileManager defaultManager] removeItemAtPath:path error:&error];
}
}
[self performSelectorOnMainThread:@selector(clearCacheSuccess) withObject:nil waitUntilDone:YES];});

-(void)clearCacheSuccess
{
NSLog(@"清理成功");
}