计算缓存大小，清楚缓存

gistfile1.m

// remove
NSFileManager *fileManager = [NSFileManager defaultManager];
if ([fileManager fileExistsAtPath:cachePath isDirectory:YES]) {
    connsuccess = [fileManager removeItemAtPath:cachePath error:nil];
}

// size bytes
- (unsigned long long)sizeForPath:(NSString *)path
{
    __block unsigned long long size = 0;
    NSFileManager *fileManager = [NSFileManager defaultManager];
    NSArray *subPath = [fileManager subpathsAtPath:path];
    [subPath enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
        BOOL isDirectory = NO;
        [fileManager fileExistsAtPath:[path stringByAppendingFormat:@"/%@", obj] isDirectory:&isDirectory];
        if (isDirectory) {
            unsigned long long subPathSize = [self sizeForPath:obj];
            size += subPathSize;
        } else {
            unsigned long long subPathSize = [[fileManager attributesOfItemAtPath:[path stringByAppendingFormat:@"/%@", obj] error:nil] fileSize];
            size += subPathSize;
        }
    }];
    return size;
}