avocado/packages/topdown/src/layers-view.js

import {Container} from '@avocado/graphics';

import LayerView from './layer-view';

export default class LayersView extends Container {

  constructor(layers, renderer) {
    super();
    this.layers = layers;
    this.layerViews = {};
    this.renderer = renderer;
    this.layers.on('layerAdded', this.onLayerAdded, this);
    for (let i = 0; i < this.layers.layers.length; i++) {
      this.onLayerAdded(this.layers.layers[i], i);
    }
    this.layers.on('layerRemoved', this.onLayerRemoved, this);
  }

  onLayerAdded(layer, i) {
    const layerView = new LayerView(layer, this.renderer);
    this.layerViews[i] = layerView;
    this.addChild(layerView);
  }

  onLayerRemoved(layer, i) {
    const layerView = this.layerViews[i];
    if (!layerView) {
      return;
    }
    this.removeChild(layerView);
  }

}