Add custom fields that influence other Checkout fields
This topic describes how to add a custom field that influences other fields on the checkout page.
Let’s consider a case where you need to add a check box whose state (selected or cleared) changes the state of other fields: when the check box is selected, the Shipping Address fields get prepopulated with a certain address. To implement such a check box, take the following steps:
Create a plugin for the process method of the <Magento_Checkout_module_dir>/Block/Checkout/LayoutProcessor.php class.
Declare the plugin in your module’s di.xml.
Create a JS component for the check box with custom logic.
Create a plugin for the LayoutProcessor’s process method
In your custom module directory, create the following new file: <your_module_dir>/Block/Checkout/SomeProcessor.php. In this file, add the following code sample. This is a plugin that adds a check box, makes the street labels trackable, and assigns dependencies to the check box.
Declare plugin in di.xml
In <your_module_dir>/etc/frontend/di.xml, declare the plugin you created on the previous step. The plugin name is arbitrary, in our example it’s ProcessAddressConfiguration:
Create a JS component for the check box
In your custom module directory, create the following new file: <your_module_dir>/view/frontend/web/js/single-checkbox.js. In this file, add the following code. This is a JS component that extends Magento_Ui/js/form/element/single-checkbox.js. The onCheckedChanged method calls the methods that update street labels, change the city and country values, and disable these fields: