I have a requirement to provide a GUI forms editor so that non-technical users can create forms. One of the tools I am looking at is the Umbraco Forms tool (formerly Umbraco Contour).
I want to be able to capture submitted data in an Action Method, process it in some way, and then send it to a web service.
Looking into the Umbraco docs, it looks as if forms generated by the Umbraco Forms tool are rendered by a macro and automatically submit data to the Umbraco database - there doesn't seem to be any way to intercept the submitted data.
Is that correct, or have I missed something?
It sounds like you need to create a custom WorkflowType. Workflows allow you to perform further actions by attaching them to certain events, i.e. when a form is submitted or approved etc. There are some options available by default for sending emails and posting data to a URL of your choice but you can add your own if these don't meet your requirements.
I suggest that you take a look at the Umbraco Forms documentation: https://our.umbraco.org/Documentation/Products/UmbracoForms
which includes a guide for adding WorkflowTypes:
https://our.umbraco.org/documentation/products/umbracoforms/Developer/Extending/Adding-a-Workflowtype