create-destroy.md

Creating and destroying nodes

Creating new nodes

Besides creating nodes by using the scene editor, we can create nodes dynamically in script. Add it into the scene by new cc.Node() to complete the whole constructive process.

Below is a simple example:

cc.Class({
  extends: cc.Component,

  properties: {
    sprite: {
      default: null,
      type: cc.SpriteFrame,
    },
  },

  start: function () {
    var node = new cc.Node('Sprite');
    var sp = node.addComponent(cc.Sprite);

    sp.spriteFrame = this.sprite;
    node.parent = this.node;
  },
});

Cloning exisiting node

Sometimes we want to clone the exisiting node dynamically in the scene, it can be done by cc.instantiate. Here is how it is done:

cc.Class({
  extends: cc.Component,

  properties: {
    target: {
      default: null,
      type: cc.Node,
    },
  },

  start: function () {
    var scene = cc.director.getScene();
    var node = cc.instantiate(this.target);

    node.parent = scene;
    node.setPosition(0, 0);
  },
});

Creating preset node

Like cloning the exisiting node, you can set a prefab and create node by cc.instantiate. Here is how it's done:

cc.Class({
  extends: cc.Component,

  properties: {
    target: {
      default: null,
      type: cc.Prefab,
    },
  },

  start: function () {
    var scene = cc.director.getScene();
    var node = cc.instantiate(this.target);

    node.parent = scene;
    node.setPosition(0, 0);
  },
});

Destroying node

Nodes can be destroyed by the function node.destroy(). It's worth mentioning that node removing will not happen immediately, but will be executed after the logic update for the present frame is complete. After a node is destroyed, it is in the invalid state. By cc.isValid, the present node can be judged whether it is destroyed or not.

Here is how to use it:

cc.Class({
  extends: cc.Component,

  properties: {
    target: cc.Node,
  },

  start: function () {
    // destroy target node after 5s
    setTimeout(function () {
      this.target.destroy();
    }.bind(this), 5000);
  },

  update: function (dt) {
    if (cc.isValid(this.target)) {
      this.target.rotation += dt * 10.0;
    }
  },
});

destroy and removeFromParent

After calling a node's removeFromParent, in-memory data is not guaranteed to be released because there may be some logical problems that cause the program to still refer to the object. So if a node is no longer used, please call its destroy instead of removeFromParent. destroy will not only activate the components onDestroy, but also reduce the probability of memory leaks, while reducing the consequences of memory leak.

In short, if a node is no longer used, use destroy, do not need removeFromParent, do not need to set parent to null.

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Continue on to read about Asset Management/Scene Management.