F# for Unity

Experimental support for F# scripting in Unity: create F# scripts with the .fs file extension and they'll be built automatically using the .NET SDK.

Features

• Automatically installs the .NET SDK locally inside your Library folder
• Automatically compiles F# scripts (.fs files) to a DLL usable by Unity
  • The DLL and its dependencies are generated at Assets/FSharpOutput. Consider ignoring this folder in your VCS (e.g.: adding to .gitignore file in Git repos).
  • The DLL references the same DLLs as Assembly-CSharp does.
  • Scripts inside Editor folders are only available in the Unity editor
• Supports defining script compilation order in the Assets/Editor/FSharpSettings asset
• Supports defining package references in the Assets/Editor/FSharpSettings asset
• Uses the same scripting symbols as C#, e.g. UNITY_EDITOR, UNITY_STANDALONE, DEVELOPMENT_BUILD, etc...
• MonoBehaviour/ScriptableObject class names do not need to have the same name as their source files. You can also declare several of them in a single file.
• The F# project is added to the solution file generated by Unity, so that Intellisense works in IDEs (tested on Visual Studio Code with Ionide extension)

How to install

Either:

• Use the openupm registry and install this package using the openupm-cli:

  openupm add com.gilzoide.fsharp
  

• Install using the Unity Package Manager with the following URL:

  https://github.com/gilzoide/unity-fsharp.git#1.0.0-preview5
  

• Clone this repository or download a snapshot of it directly inside your project's Assets or Packages folder.

Creating scripts in F#

// 1. Add a namespace to your file
namespace MyFSharpNamespace

// 2. Import the UnityEngine and other namespaces as necessary
open UnityEngine

// 3. Create classes that inherit from MonoBehaviour, as usual
type MyFSharpComponent() =
  inherit MonoBehaviour()

  // Use mutable serialized fields to edit them in the Inspector
  [<SerializeField>]
  let mutable serializedFloat = 5f

  [<SerializeField>]
  let mutable prefab: GameObject = null

  [<SerializeField>]
  let mutable intArray: array<int> = [||]

  // In F#, lists are immutable by default and not serialized by Unity
  // Use ResizeArray (a.k.a. System.Collections.Generic.List) to serialize lists
  [<SerializeField>]
  let mutable intList = new ResizeArray<int>()

  // Declare member functions (a.k.a. methods)
  member this.Start() =
    // In F#, we mutate fields with `<-` instead of `=`
    serializedFloat <- 10f

    // In F#, use `isNull` and `isNotNull` to check for null Objects
    if isNotNull prefab then
      Object.Instantiate(prefab, this.transform) |> ignore

F# Settings asset

The asset Assets/Editor/FSharpSettings.asset is created automatically and contains the following settings:

• Script Compile Order: this list contains all F# script assets that will be compiled. Freely reorder the scripts to ensure the correct compilation order in the F# project. Tip: keep FSharpGlobals.fs first.
• Package References: add NuGet package references to the F# project. The package DLLs will be automatically copied to the Assets/FSharpOutput directory by the build.