iOS开发，清除缓存功能在iOS8上有效，在iOS9和10上无效

// 清理缓存
    NSString *cachePath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    NSArray *files = [[NSFileManager defaultManager] subpathsAtPath:cachePath];
    NSLog(@"文件数 ：%ld",[files count]);
    for (NSString *p in files)
    {
        NSError *error;
        NSString *path = [cachePath stringByAppendingString:[NSString stringWithFormat:@"/%@",p]];
        if([[NSFileManager defaultManager] fileExistsAtPath:path])
        {
            [[NSFileManager defaultManager] removeItemAtPath:path error:&error];
        }
    }