How to Recursively Render Components in Owl

In the dynamic landscape of web development, the orchestration of complex hierarchical data structures is both an art and a science. Enter Owl.js, a framework inspired by React, offering developers a seamless solution for rendering parent-child relationships in a recursive and elegant manner. In this blog, we will take a deep dive into Owl.js' recursive rendering capabilities, exploring the intricacies of the code alongside a representative hierarchical data structure.

Let’s Make a Recursive Component

const { xml, Component } = owl;
class RecursiveComponent extends Component {
 // Some Logic
 static template = xml`
 <div t-att-style="props.value.style" style="width: 400px;height: 150px;">
   <t t-out="props.value.name"/>
   // some content
 </div>
}

Here we have created a Component. The template static property of the Recursive Component defines its structure. The t-att-style directive is used to dynamically set the style based on the style property of the data. Now, let's see how we can use it in Real Action.

Using the RecursiveComponent

const { xml, Component, reactive, useState, mount } = owl;
const hierarchicalData = reactive([
  {
    id: 1,
    name: "Parent 1",
    style: "transform: translateX(0px);",
    children: [
      {
        id: 2,
        name: "Child 1-1",
        style: "transform: translateX(50px);",
        children: [
          {
            id: 3,
            name: "Grandchild 1-1-1",
            style: "transform: translateX(100px);",
            children: [],
          },
          // ... more grandchildren
        ],
      },
      // ... more children
    ],
  },
  // ... more parents
]);
class ParentComponent extends Component {
  setup() {
    this.state = useState(hierarchicalData);
    onMounted(() => this.renderChild(this.state));
    this.root = useRef("root");
  }
  async renderChild(data) {
    for (const value of data) {
      await mount(RecursiveComponent, this.root.el, {
        props: {
          value,
        },
        env: this.env,
      }).then(async () => {
        if (value.children.length) {
          await this.MountChild(value.children);
        }
      });
    }
  }
  static template = xml
    <div class="container">
      <div t-ref="root"/>
    </div>
}

The code begins by importing necessary modules and functions from the Owl.js framework.

Notable imports include xml for defining templates, Component for creating components, reactive for creating reactive data, useState for managing component state, and mount for rendering components.

A reactive object is used to create a hierarchical data structure. This structure represents parents, children, and grandchildren, each with an id, name, style, and potentially children property. The renderChild method is responsible for rendering child components using the mount function.

It iterates through the provided data array, creating instances of RecursiveComponent for each item.

If a data item has children, the method recursively calls itself to render the grandchildren.

Understanding the Recursive Rendering Journey

1. Iterating Through Hierarchical Data

The for...of loop gracefully traverses the hierarchical data, symbolizing the essence of parent-child relationships.

2. Mounting the RecursiveComponent

The mount function takes center stage, rendering an instance of RecursiveComponent for each data item. This component becomes a canvas for dynamic content.

3. Passing Essential Props

Crucial props, including the current data item (value) and a reference to overarching data (data), are passed to each RecursiveComponent. This ensures each component is equipped with the necessary information.

4. Recursion for Child Components

As the rendering unfolds, a moment of brilliance occurs. The function checks if the current data item has children (value.children.length). If so, it takes a bow and gracefully calls itself (this.MountChild) to render child components. This recursive dance continues until every leaf of the hierarchical tree has been adorned with its own component.

In the enchanting realm of Owl.js, recursive component rendering emerges as a symphony—an intricate dance that elegantly transforms hierarchical data into a visual masterpiece. As you embark on your journey with Owl.js, let the MountChild function guide your steps, bringing life and order to the rich tapestry of parent-child relationships in your web applications. May your components dance in unison, harmonizing with the rhythms of your data structures and creating a truly immersive and dynamic user experience. If you want to know more about Owl components in odoo, refer to our previous blog.