Custom Signals#

A Signal source adds one way to produce or write an existing value type. Once discovered, it works in every field that accepts that type.

Adding a source to an existing type#

Derive from the type's abstract base, such as TypeNumber, TypeString, or TypeGameObject, and override Get. This example assumes MyComponent exposes a numeric Value property:

using System;
using UnityEngine;
using VisualScript.Icons;
using VisualScript.Runtime;

[Get]

[Title("My Value")]
[Category("My System/My Value")]
[Description("The current value of the custom system")]

[Image(typeof(IconNumber), ColorTheme.Type.Teal)]

[Serializable]
public class TypeNumberMyValue : TypeNumber
{
    [SerializeField] private GetGameObject m_Source = new GetGameObject();

    public override double Get(Args args)
    {
        MyComponent component = this.m_Source.Get<MyComponent>(args);
        return component != null ? component.Value : 0d;
    }

    public override string ToString() => $"{this.m_Source} value";
}

Get returns the component's Value, or 0 when the resolved object has no MyComponent. Three parts define the source's editor and runtime behavior:

• [Get] adds the type to Get dropdowns. Add [Set] and override Set for a writable source.
• Get(Args) produces the value from the current context.
• ToString() returns the phrase shown in the collapsed field.

Writable sources#

Add [Set] and implement Set only when the underlying value is writable. This partial example keeps the source field and Get implementation from the previous example:

[Get] [Set]

[Serializable]
public class TypeNumberMyValue : TypeNumber
{
    public override double Get(Args args) { /* … */ }

    public override void Set(double value, Args args)
    {
        MyComponent component = this.m_Source.Get<MyComponent>(args);
        if (component != null) component.Value = value;
    }
}

Set writes the supplied value when MyComponent exists. Leave [Set] off read-only sources so designers don't select a write operation that can't change the value.

Signals must be pure#

Like Conditions, Get can be called many times per frame. A binding may read it every frame for each subscription, so reading a Signal must not change state.

Evaluation cost matters for the same reason. If a binding polls a Get that raycasts, it repeats that raycast every frame.

Reporting changes#

Override Subscription to declare how the Signal detects change. This is what makes On Number Change work with your source. Choose the mode based on the available notifications and evaluation cost:

Use OnChange to poll a cheap Get implementation:

protected override SubscriptionMode Subscription => SubscriptionMode.OnChange;

OnChange reads the value every frame and notifies subscribers when it differs. When the underlying source already raises an event, use Custom to avoid that polling. Override OnSubscribe to register the callback and return its subscription Guid, then release it in OnUnsubscribe.

Editor previews#

GetPreview(GameObject source) returns a value for the Inspector outside Play mode. Implement it when the field would otherwise give no indication of its result.

Adding a whole new value type#

A new value type requires four pieces:

1. An abstract TypeMyThing : TType<MyThing> base.
2. A GetMyThing : TSignalGet<TypeMyThing, MyThing> wrapper, and SetMyThing if it's writable.
3. At least one concrete source — usually a constant and a variable lookup.
4. An editor drawer implementing ITypeDrawer so the field renders properly.

Reserve this work for a type used throughout the project. For one field, prefer a Scriptable Object Signal or a Game Object Signal that resolves a component.

Checklist#

• [Serializable], derived from the matching Type… base.
• [Get], [Set], or both, with matching overrides.
• Get is pure and proportionately cheap.
• ToString() returns a readable phrase.
• Subscription matches the source's change mechanism and cost.

Where to go next#

• Bindings — follow subscription modes from the designer's perspective.
• Custom variable types — add a value type that variables can store.
• Custom Conditions — implement a synchronous guard around a Signal.