计算空间大小

+ (long long)fileSizeAtPath:(NSString*)filepath
{
    NSFileManager* manager = [NSFileManager defaultManager];
    if ([manager fileExistsAtPath:filepath]){
        return [[manager attributesOfItemAtPath:filepath error:nil] fileSize];
    }
    return 0;
}

/*
 *FOUNDATION_EXPORT NSString * const NSFileSystemSize;//系统总空间大小
 *FOUNDATION_EXPORT NSString * const NSFileSystemFreeSize;//系统可使用空间大小
 */
+ (CGFloat)getStorage
{
    NSDictionary *fattributes = [[NSFileManager defaultManager] attributesOfFileSystemForPath:NSHomeDirectory() error:nil];
        NSNumber *num = [fattributes objectForKey:NSFileSystemFreeSize];
        return [num longLongValue]/1024.0/1024.0/1024.0;
}