Gdscript automatically assigns a value to a variable when it specifies its type

yufengjie97 · August 8, 2024, 1:16pm

I found something interesting in gdscript.

gentlemanhal · August 9, 2024, 7:06pm

I believe this is due to the fact GDScript doesn’t have nullable types. For example var s: String = null generates an error.

Possibly some more info

github.com/godotengine/godot-proposals

Add support for nullable static types in GDScript

opened 01:53AM - 16 Oct 19 UTC

aaronfranke

topic:gdscript requires core feedback

**Describe the project you are working on:** This applies to many projects. This… is an offshoot from https://github.com/godotengine/godot-proposals/issues/737, example use cases and other discussions are welcome. **Describe the problem or limitation you are having in your project:** Let's say you have a method that accepts a 2D position, which would look something like this: ```gdscript func whatever(vec): ``` A problem with this is that there's no type safety, so the function could unexpectedly break if the passed-in value is not a `Vector2`. One option is to use static typing: ```gdscript func whatever(vec: Vector2): ``` This works, and now it's not possible for users to, for example, pass in a `Color` or any other type that's invalid for this method. However, now you can't pass in `null` to mean N/A or similar. **Describe how this feature / enhancement will help you overcome this problem or limitation:** If GDScript's static typing system allowed specifying nullable types, we would be able to restrict the type to either a valid value or `null`. The presence of a valid value can then be detected simply by checking if it is not null, as non-null nullable typed values must be valid values. **Show a mock up screenshots/video or a flow diagram explaining how your proposal will work:** My suggestion is to simply allow this by adding a question mark after the type name, which is the same syntax used in C#, Kotlin, and TypeScript. User code could look something like this: ```gdscript func whatever(vec: Vector2?): ``` **Describe implementation detail for your proposal (in code), if possible:** Aside from the above, I don't have any specific ideas on how it would be implemented. However, I will add that we could expand this idea for engine methods. Many parts of Godot accept a specific type or `null` to mean invalid or N/A, or return a specific type or `null` when there is nothing else to return. For example, `Plane`'s [intersect methods](https://docs.godotengine.org/en/latest/classes/class_plane.html#class-plane-method-intersect-3) return a `Vector3` if an intersection was found, or `null` if no intersection was found. Nullable static typing could essentially self-document such methods by showing that the return type is `Vector3?` instead of `Vector3`. **If this enhancement will not be used often, can it be worked around with a few lines of script?:** The only option is to not use static typing if you need the variable to be nullable. **Is there a reason why this should be core and not an add-on in the asset library?:** Yes, because it would be part of GDScript.

sancho2 · August 10, 2024, 7:03am

You should be getting warnings about this though:

The variable "a" was used but never assigned a value.
  <GDScript Error>UNASSIGNED_VARIABLE

pennyloafers · August 11, 2024, 11:25am

If you want the office explaination.

Built in types are passed by value, and null isn’t a value.

Everything else can be passed by reference, and can have a null reference.