Heartstone like draggable attack system

Hi all,
I need some advice how to implement an attack system heartstone like (a screen below). It is a draggable arrow from the start point to the point where I realease it.

How I can start to do this?

Thanks for any suggest

Save the point where you first tap, or just have a default centered point for an object and get that. Then have an arrow tip image follow your finger with update. Then to connect them, have a simple line image that constantly updates and stretches and itself between both points. If you want to have a dashed line that looks consistent, you could have a mask that stretches while both rotate.