cisco router as DHCP server with multiple vlans

The best way to do it is I believe what Chris described, i.e using a trunk link.

However, even if a trunk link is not used on the router. We could connect one access port from each VLAN to a seperate physical router interface. Once the correct IPs are specified on those interfaces, the router's DHCP server would automatically map each DHCP pool to the correct interface. Thus eleminating the need for an IP helper.

Now, I'm not sure what happens if we configure the switch as a DHCP server instead of the router, If it can't map the pools automatically, we might need an IP helper there. got to expriment with that

Please correct me if I'm wrong.