how would this magic item created work by raw?

[morkendi]

Ring created would be Hide from undead which is a first lvl cleric spell. Continuous would be
Spell level × caster level × 2,000 gp x1.5 because base spell is 10 min./level.

I pissed of a player because I said when he attacks, he still becomes visible until the beginning of his next turn. At that point the ring would make him invisible again if he did not attack. He thinks he should be inviso as soon as he finishes his actions. I tried to explain that if he attacks, the turn system is designed to replicate people trying to trade blows and that the ring wont be able to activate until he breaks that in some way like holding, taking a move action or any action that does not involve attacking first. It would not cost him an action, but it can not change the spell used to create it. The only other option would be forcing it to be use activated as the cost would be the same. This would cause him to use an action so he could attack and then turn inviso, but then he would not be able to move and the intelligent undead may have an idea where he is. I just wanted another opinion on this.

[Troacctid]

By RAW, you really don't want it to be continuous. The spell ends when you attack, and if you have no way of reactivating the item, it is now useless forever.

I'd recommend a shirt of wraith stalking instead.

[John Longarrow]

You could always just let them know "This is how it works in my game".

[Inevitability]

You could always just let them know "This is how it works in my game".

In that case at least let the player swap it out, though. They bought the item with certain assumptions about how the game was going to work: they deserve to undo the purchase if those assumptions are no longer correct.