Trying CC Simple Wire Removal with Null objets

[AlbertLiving]

I'm trying to animate the effect of CC Simple Wire Removal by parenting the 2 endpoints (A & B) to 2 Null Objects for left and right, and these to a last Null Object that would allow me to move both at the same time. 

But this last step seems to fail and the effect stays in a corner of the composition, not allowing me to move it with any Null Object.

[Dan Ebberts · Accepted solution]

Try changing your expressions to this:

L = thisComp.layer("RIGHT");
L.toComp(L.anchorPoint)

and this:

L = thisComp.layer("LEFT");
L.toComp(L.anchorPoint)

[AlbertLiving]

SOLVED.

Why? Just why...
I don't understand much about expressions, but I thought it would be simple to do something like parent null to null... I don't know, if you could explain it to me, it would help me a lot to understand, thank you very much.

[Dan Ebberts]

When you parent one layer to another, its position is no longer given in comp coordinates--it becomes relative to the parent's upper left corner (usually). To get the parented layer's actual position in comp coordinates, you have to use a layer space transform expression. It can be a little tricky to understand until you get the hang of it.