derive host address from network

[RubyTuesdayDONO]

given a network and a host portion, is it possible for IPAddress to generate the full host address in that network? for example, if i've got an IPAddress('1.1.1.0/24'), can i ask it for the full address of a host whose host bits are 123 (i.e. 1.1.1.123)?

i searched various methods and did not see anything direct (yes, you can splice octets, but that only works reliably for /8, /16, and /24 networks). there are useful applications in templating, e.g. "i'm planning IPs for a new network, and hosts of a given role always have the host bits 123, so please give me the full address of that host in this network"