is there a way to prevent apps from seeing my contacts

If Apps require access to contacts, they will request it via a popup when you open them the first time, and you can deny it at that point.

You can see any Apps that have requested access to contacts in the past in Settings->Privacy->Contacts and revoke that access by turning off the switch there.

If the app does not appear there, it has not requested access to contacts and as such does not have access to them.

On iOS, go to Settings -> Privacy -> Contacts and turn the slider to the off position on any apps you don't want access to the contacts stored on your iPhone.