Call a function in another codefile

[Dziriki]

Hello, I am relatively new to programming in LUA. I cannot figure out how to call a function located in a secondary .lua file inside the addon folder.

I have 3 files in the folder.
addon.lua
objectfactory.lua
RiftAddon.toc

I add both lua files to RiftAddon "RunAtStartup" section.
But every time I try to call a function in objectfactory I get this error:

Error: attempt to index global "function" (a nil value) In addon/addon.lua

Any advice would be greatly appreciated.