custom component command message

Hello,

I am currently working on creating a custom date picker component with the vertigis web SDK. I am having trouble understanding the docs on how to create a command message that emits the date when a new date is selected. 

In normal JS I would just have an useEffect hook that would emit the date once the newDate variable is selected by the date picker. The process with vertigis is different. There seems to be a couple ways to do this from the docs, but none seem very straight forwards for what im trying to do. Im not entirely sure if i need to use a UIContext, useSubscribe or useWatch .

Any help would be great, Thank you!