An experiment if Unity3D and (kind of) idiomatic F# can play nicely together.

functional_unity3d.fsx

#r @"C:\Users\TBurger\Downloads\UnityEngine.dll"

open UnityEngine

module Unity =

    [<AutoOpen>]
    module Log =
        let inline uprintfn fmt =
            Printf.kprintf Debug.Log fmt
        let inline uwprintfn fmt =
            Printf.kprintf Debug.LogWarning fmt
        let inline ueprintfn fmt =
            Printf.kprintf Debug.LogError fmt
            
    type Update = unit -> unit
    type FixedUpdate = unit -> unit
    type Updater = Update * FixedUpdate
    type Awake = unit -> Updater
    type Startup = unit -> Awake

    let inline skipAwake update fixedUpdate: Awake = fun () -> update, fixedUpdate
    let inline onlyUpdate update: Updater = update, id
    let inline onlyFixedUpdate fixedUpdate: Updater = id, fixedUpdate
    let skipUpdates: Updater = id, id

    type [<AbstractClass>] FunBehaviour(startup: Startup) =
        inherit MonoBehaviour()
        let mutable awake, update, fixedUpdate =
            Unchecked.defaultof<Awake>,
            Unchecked.defaultof<Update>,
            Unchecked.defaultof<FixedUpdate>
        member __.Start() = awake <- startup()
        member __.Awake() =
            let u, fu = awake()
            update <- u
            fixedUpdate <- fu
        member __.Update() = update()
        member __.FixedUpate() = fixedUpdate()

(* USAGE *)

open Unity

type FSSimpleComponent() as self =
    inherit FunBehaviour(fun () ->
        uprintfn "in init of %O" self
        let rigidbody = self.GetComponent<Rigidbody>()
        let inline update () =
            //uprintfn "in update of %O" self
            rigidbody.transform.Rotate(Vector3(1.f, 1.f, 1.f) * self.speed * Time.deltaTime)
        skipAwake update id)
    member val speed = 2.0f with get, set

type FSOtherComponent() as self =
    inherit FunBehaviour(fun () () ->
        uprintfn "in awake of %O" self
        let otherComponent = self.GetComponent<FSSimpleComponent>()
        let otherComponentsRigidbody = otherComponent.GetComponent<Rigidbody>()
        uprintfn "%f: %s" otherComponent.speed otherComponentsRigidbody.name
        skipUpdates)