Collision code sample not working

[aphixe]

I copied the script example to do collision test. and unity says it can't convert out from the collider

Assets/Scripts/GrabRope.cs(33,64): error CS1503: Argument `#2' cannot convert `out UnityEngine.Collider' expression to type `out UnityEngine.Component'


 Collider collider;
if (ObiCollider.idToCollider.TryGetValue(contact.other,out collider)){
// do something with the collider.
}

i looked at CollisionEventHandler and it uses Component collider;  is that what it should be? 

all i know is its not working. trying for a long time today to code a grab the rope script