What's the best approach to draw lines between views?

Background: I have a custom scrollview (subclassed) that has uiimageviews on it that are draggable, based on the drags I need to draw some lines dynamically in a subview of the uiscrollview. (Note I need them in a subview as at a later point i need to change the opacity of the view.)

So before I spend ages developing the code (i'm a newbie so it will take me a while) I looked into what i need to do and found some possible ways. Just wondering what the right way to do this.

1. Create a subclass of UIView and use the drawRect method to draw the line i need (but unsure how to make it dynamically read in the values)
2. On the subview use CALayers and draw on there
3. Create a draw line method using CGContext functions
4. Something else?

Cheers for the help