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Extending React.js components

Posted by: admin November 30, 2017 Leave a comment

Questions:

One of the things I appreciate the most about Backbone.js is how simple and elegant inheritance works. I’m starting to get to grips with React, and can’t really find anything in react that resembles this Backbone code

var Vehicle = Backbone.View.extend({
    methodA: function() { // ... }
    methodB: function() { // ... }
    methodC: function() { // ... }
});

var Airplane = Vehicle.extend({
    methodC: function() {
        // Overwrite methodC from super
    }
});

In react we have mixins, and using those we could get somewhat close to the above example if we went like this

var vehicleMethods = {
    methodA: function() { // ... }
    methodB: function() { // ... }
}

var Vehicle = React.createClass({
    mixins: [vehicleMethods]
    methodC: function() { 
        // Define method C for vehicle
    }
});

var Airplane = React.createClass({
    mixins: [vehicleMethods]
    methodC: function() {
        // Define method C again for airplane
    }
});

This is less repetitive than defining the same stuff over and over again, but it doesn’t seem to be nearly as flexible as the Backbone way. For instance, I get an error if I try to redefine/overwrite a method that exists in one of my mixins. On top of that, the React.js way is more code for me to write.

There is some incredibly clever stuff in react, and it feels like this is more the case of me not getting how to properly do this, than it feels like a feature missing from React.

Any pointers are greatly appreciated.

Answers:

To get something that resembles inheritance (actually composition as pointed out in comments), you can make an Airplane in your example wrap itself in a Vehicle. If you want to expose methods on Vehicle in the Airplane component, you can use a ref and connect them one-by-one. This is not exactly inheritance (it’s actually composition), particularly because the this.refs.vehicle will not be accessible until after the component has been mounted.

var Vehicle = React.createClass({
    ...
});

var Airplane = React.createClass({
    methodA: function() {
      if (this.refs != null) return this.refs.vehicle.methodA();
    },
    ...
    render: function() {
        return (
            <Vehicle ref="vehicle">
                <h1>J/K I'm an airplane</h1>
            </Vehicle>
        );
    }
});

Also it’s worth mention that in the React official documentation they prefer composition over inheritance:

So What About Inheritance? At Facebook, we use React in thousands of
components, and we haven’t found any use cases where we would
recommend creating component inheritance hierarchies.

Props and composition give you all the flexibility you need to
customize a component’s look and behavior in an explicit and safe way.
Remember that components may accept arbitrary props, including
primitive values, React elements, or functions.

If you want to reuse non-UI functionality between components, we
suggest extracting it into a separate JavaScript module. The
components may import it and use that function, object, or a class,
without extending it.

Another thing worth mention that using ES2015/ES6+ you can also spread the object props from Airplane component to the Vehicle component

render: function() {
    return (
        <Vehicle {...this.props}>
            <h1>J/K I'm an airplane</h1>
        </Vehicle>
    );
}

Questions:
Answers:

If you use webpack+babel+react NPM package set up in your project, then in ES6 OOP implementation it should be as simple as this:

import React, { Component } from 'react';
import ReactDOM from 'react-dom';

class BaseComponentClass extends Component {
  componentDidMount() {} 
  render() { return (<div>Base Component</div>) }
}
class InheritedComponentClass extends BaseComponentClass {
  // componentDidMount is inherited
  render() { return (<div>Inherited Component</div>) } // render is overridden 
}
ReactDOM.render(<InheritedComponentClass></InheritedComponentClass>, 
     document.getElementById('InheritedComponentClassHolder'));

Note: Here is a simple starter kit with such set up: https://github.com/alicoding/react-webpack-babel

Questions:
Answers:

By leveraging ReactOO, you can easily use inheritance (Disclaimer: I’m the author of ReactOO):

(function () {

    // Class definitions. ReactOO requires class definition first just like you did in an OO way.

    window.Vehicle = window.ReactOO.ReactBase.extend({
        getReactDisplayName: function () {
            return 'Vehicle';
        },

        onReactRender: function (reactInstance) {
            var self = this;

            var text = self.methodC();

            return React.createElement('div', {}, text);
        },

        methodA: function () {
            console.log('Vehicle method A');
        },

        methodB: function () {
            console.log('Vehicle method B');
        },

        methodC: function () {
            return 'Vehicle method C';
        }
    });

    window.Airplane = window.Vehicle.extend({
        getReactDisplayName: function () {
            return 'Airplane';
        },

        methodC: function () {
            // Call this._super() to execute parent method.
            //this._super();
            return 'Airplane method C';
        }
    });

    var vehicle = new window.Vehicle();
    vehicle.render({}, '#vehicle');

    var airPlane = new window.Airplane();
    airPlane.render({}, '#airPlane');
})();
<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <title>ReactOO Vehicle-Aireplane Example</title>
    <link rel="stylesheet" href="css/base.css" />
    <script src="scripts/react.js"></script>
    <script src="scripts/react-dom.js"></script>
    <script src="../src/reactoo.js"></script>
</head>
<body>
    <div id="vehicle">
    </div>
    <div id="airPlane">
    </div>
    <script src="scripts/vehicleAirplane.js">
    </script>
</body>
</html>

enter image description here

Questions:
Answers:

I think extending may be done with using jQuery.extend or similar

Base.jsx

module.exports = {
    methodA:function(){
        ...
    }
}

Child.jsx

var Base = require('./Base.jsx');

module.exports = React.createClass($.extend({},Base,{
    methodB:function(){
        ...
        this.methodA();
        ...
    },
    render:function(){
        return ...
    }
}));