Common Node and Component Interfaces

Common Node and Component Interfaces

After obtaining a Node or Component instance through the method introduced in the Access Node and Component documentation, there are common interfaces that can be used to achieve the various effects needed through the node and component instance and it’s operation.

Please review the Node and the Component API documentation.

Node Status and Level Operations

Suppose you are inside a running component script, to access a node inside the current script use this.node.

Activating and Deactivating a Node

A node is activated by default. It’s activation state can be changed in code by setting the node’s active property. Example:

this.node.active = false;

Setting the active property and switching the active and closed states of the node in the editor have the same effect. When a node is down, all its components will be disabled. At the same time, all its child nodes and components on the child nodes will also be disabled. It should be noted that when child nodes are disabled, their active properties are not changed, so they will return to their original state when the parent node is reactivated.

In other words, active actually represents the active state of the node itself, and whether this node current can be activated depends on its parent node. And if it is not in the current scene, it cannot be activated. We can use the read-only property activeInHierarchy on the node to determine whether it is currently activated. Example:

this.node.active = true;

If the node is in the can be activated state, modifying active to true will immediately trigger the following activation operations:

Reactivate the node and all child nodes under the node whose active is true in the scene
All components on this node and all child nodes will be enabled, and the update method in them will be executed every frame afterwards
If there are onEnable methods on these components, these methods will be executed
```
this.node.active = false;
```

If the node is already activated, changing active to false will immediately trigger the following shutdown operations:

Hide the node and all child nodes under the node in the scene
All components on this node and all child nodes will be disabled, that is, the code in update in these components will no longer be executed
If there are onDisable methods on these components, these methods will be executed

Change the Parent Node of a Node

Suppose the parent node is parentNode and the child node is this.node.

This is valid:

// method 1
this.node.parent = parentNode;

This is also valid:

// method 2
this.node.removeFromParent();
parentNode.addChild(this.node);

These two methods are equivalent.

Notes:

The removeFromParent usually needs to pass a false, otherwise it will empty the bound events and actions, etc. on the node by default.
After creating a new node through the method introduced in the Create and Destroy Node documentation, it is a must to set a parent node for the node to correctly initialize the node.

Child Nodes of the Parent Node

this.node.children will return an array of all child nodes of the node.

this.node.children.length will return the number of children of the node.

Note: the above two APIs will only return the direct child nodes of the node, not the child nodes of the child node.

Changing Node Transformations (position, rotation, scaling)

Changing Node Location

There are two ways:

Use the setPosition method:

 this.node.setPosition(100, 50, 100);
 // Or
 this.node.setPosition(new Vec3(100,50,100));

Setting the position variable:

 this.node.position = new Vec3(100,50,100);

The above two usages are equivalent.

Changing Node Rotation

Example:

this.node.setRotation(quaternion);

Or set local rotation by Euler angle:

this.node.setRotationFromEuler(90,90,90);

Changing Node Scale

Example:

this.node.setScale(2,2,2);

Common Component Interface

Component is the base class of all components, and any component includes the following common interfaces (assuming that we use this to refer to this component in the script of the component):

this.node: The node instance to which this component belongs.
this.enabled: Whether to execute the update method of the component every frame, and also to control whether the renderable component is displayed.
update(deltaTime: number): As a member method of the component, when the component’s enabled property is true, the code in it will be executed every frame.
onLoad(): Executed when the node where the component is located is initialized (when the node is added to the node tree).
start(): It will be executed before the first update of the component, usually used for logic that needs to be executed after the onLoad of all components is initialized.