ios获得本机可用存储空间大小

#include <sys/param.h>
#include <sys/mount.h>
/**
 获取系统剩余存储空间大小
 @return MB
 */
+ (double)freeDiskSpaceInBytes;

+ (double)freeDiskSpaceInBytes{
    struct statfs buf;
    unsigned long long freeSpace = -1;
    if (statfs("/var", &buf) >= 0) {
        freeSpace = (unsigned long long)(buf.f_bsize * buf.f_bavail);
    }
    return freeSpace/1024/1024;
}