Whether or not the cops arrest you depends entirely on how they are approached. Unfortunately, they vary from town to town and maybe even shift to shift.

Thankfully, the police probably aren't the only option available.

If your domestic partner is violently abusing you, you are a victim of domestic violence. There are social services in virtually any country where it's not legal to just slap your spouse, to help stop the slapping to stop. Places to start looking:

1. A domestic violence advocacy group.
2. A social-good organization, like a local church or food bank.
3. Your employer's HR department.
4. Your doctor.
5. Your lawyer.

All of the above should either have someone they can refer you to, or be able to help you themselves. If you have a lawyer on retainer you definitely should call them first, and if you have decent health care your GP doctor or an urgent care should be able to check how badly you're hurt and document the violence.

If all else fails, go to your local police department and tell them you want to report a crime. Or just leave and crash with family or a friend.

If your partner hits you and tells you that you'd be arrested if you call the cops on them, they are telling you that they will do it again and lie about it.