'Required if' Validation in Sitecore Forms

Question

Is there any recommended way to configure 'Required if' Validation in Sitecore Forms?

For example, field A is required if checkbox B is ticked?

At the moment for most form elements I seem limited to optional or mandatory:

Is the answer just to build a custom validator for each input type? I am using Sitecore 9 Update 1

Answer 1

At the moment, that is not possible ootb. So you will need a custom validation. My own blog post could be a start (https://ggullentops.blogspot.com/2017/10/sitecore-9-forms-custom-validation.html) but there is also documentation on the Sitecore docs (https://doc.sitecore.com/developers/91/sitecore-experience-management/en/walkthrough--creating-a-custom-validation.html).

Try to make you validation a bit generic - e.g. add the checkbox B as a parameter so you can reuse the validator on multiple forms..

ps: and if you wrote this conditional validation, sharing it with the community would be appreciated ;)