Implement a QR Code Custom Form Element using a Third Party Library

Implementing a custom form element allows you to augment the existing form elements that come with VertiGIS Studio Workflow.

This article will walk you through creating a form element that uses the qrcode library to generate and display a QR code.

Prerequisites

Follow the instructions in the Web Applications SDK page to set up your development environment.

note

A working knowledge of TypeScript is recommended before extending Workflow for web-based hosts.

Overview

Implementing a QR code custom form element for web applications using a third party library consists of the following steps:

1. Adding third party library dependencies to your project.
2. Creating the custom form element.
3. Implementing the custom form element using the third party library.

Adding Dependencies

1. Run npm install qrcode in the terminal to install the third party qrcode library that generates QR codes.
2. Run npm install @types/qrcode in the terminal to install type information for the third party library. This is optional, but it provides an improved developer experience.

Set up Custom Form Element Skeleton

To create a new form element:

1. Open the Workflow activity SDK in Visual Studio Code.
2. Run npm run generate in the terminal.
3. When prompted, select Form Element.
4. Enter the name of the form element you would like to create and press Enter. For example, QrCode.
5. Open the newly created src/elements/QrCode.tsx file.

Implement the Custom Form Element

Modify the skeleton form element implementation in src/elements/QrCode.tsx to match the following example.

src/elements/QrCode.tsx

import * as React from "react";
import { useEffect, useState } from "react";
import QRCode from "qrcode";
import {
    FormElementProps,
    FormElementRegistration,
} from "@vertigis/workflow";

interface QrCodeProps extends FormElementProps<string> {}

function QrCode(props: QrCodeProps): React.ReactElement | null {
    const { value } = props;
    const [qrCodeUrl, setQrCodeUrl] = useState("");

    // Update the QR code when the value changes
    useEffect(() => {
        // Clear the previous QR code
        setQrCodeUrl("");
        if (value) {
            // Asynchronously generate the QR code data URL from the value
            let didCancel = false;
            (async () => {
                const dataUrl = await QRCode.toDataURL(value);
                if (didCancel) {
                    return;
                }
                setQrCodeUrl(dataUrl);
            })();
            return () => {
                didCancel = true;
            };
        }
    }, [value]);

    // Render the QR code as an image
    return qrCodeUrl ? <img src={qrCodeUrl} /> : null;
}

const QrCodeElementRegistration: FormElementRegistration<QrCodeProps> =
    {
        component: QrCode,
        getInitialProperties: () => ({ value: "" }),
        id: "QrCode",
    };

export default QrCodeElementRegistration;

Deploy the Form Element

Follow the instructions to build and deploy the activity pack.

Test the Form Element

Once your activity pack is hosted and registered, your QrCode custom form element should appear in the form element toolbox in VertiGIS Studio Workflow Designer alongside the built-in form elements.

To use your custom form element in a workflow:

1. Select the Display Form activity that you want to include your form element in.
2. Locate the QrCode form element in the toolbox and drag it onto the form.
3. Alternatively:
   1. Add a Custom form element to the form.
   2. Set the Custom Type property of the Custom form element to QrCode.
4. Add a load event subworkflow to the form element.
5. Add a Set Form Element Property activity to the subworkflow.
6. Set the Property Name input to value.
7. Set the Property Value input to the text that represents the data or URL to encode into the QR code.
8. Test your workflow.

Next Steps

Learn how to create a QR Code activity

Learn how to to use this same third party library to create an activity that creates QR codes

Get Started