The following table contains available Typescript decorators that Needle Engine provides.
You can think of them as Attributes on steroids (if you are familiar with C#) - they can be added to classes, fields or methods in Typescript to provide additional functionality.
Field & Property Decorators | |
@serializable() | Add to exposed / serialized fields. Is used when loading glTF files that have been exported with components from Unity or Blender. |
@syncField() | Add to a field to network the value when it changes. You can pass in a method to be called when the field changes |
@validate() | Add to receive callbacks in the component event method onValidate whenever the value changes. This behaves similar to Unity's onValidate. |
Method Decorators | |
@prefix(<type>) (experimental) | Can be used to easily inject custom code into other components. Optionally return false to prevent the original method from being executed. See the example below |
Class Decorators | |
@registerType | No argument. Can be added to a custom component class to be registered to the Needle Engine types and to enable hot reloading support. |
Examples
Serializable
export class ButtonObject extends Behaviour {
// you can omit the type if it's a primitive
// e.g. Number, String or Bool
@serializable()
myNumber: number = 42;
// otherwise add the concrete type that you want to serialize to
@serializable(EventList)
onClick?: EventList;
@serializable(SomeComponentType)
myComponent: SomeComponentType;
// Note that for arrays you still add the concrete type (not the array)
@serializable(Object3D)
myObjects: Object3D[];
}
SyncField
export class MyScript extends Behaviour {
@syncField(MyScript.prototype.onNumberChanged)
@serializable()
myNumber: number = 42;
private onNumberChanged(newValue : number, oldValue : number){
console.log("Number changed from ", oldValue, "to", newValue)
}
}
Validate
export class MyScript extends Behaviour {
@validate()
@serializable()
myNumber?: number;
start() { setInterval(() => this.myNumber = Math.random(), 1000) }
onValidate(fieldName: string) {
console.log("Validate", fieldName, this.myNumber);
}
}
Prefix
import { Camera } from "@needle-tools/engine";
class YourClass {
@prefix(Camera) // < this is type that has the method you want to change
awake() { // < this is the method name you want to change
// this is now called before the Camera.awake method runs
// NOTE: `this` does now refer to the Camera instance and NOT `YourClass` anymore. This allows you to access internal state of the component as well
console.log("Hello camera:", this)
// optionally return false if you want to prevent the default behaviour
}
}