density
The relative mass density of the behavior’s dynamic items.
Declaration
var density: CGFloat { get set }Discussion
A dynamic item’s relative density, along with its size, determines its effective mass when it participates in UIKit Dynamics behaviors—including friction, collisions, pushes, and so on. For example, say you have two dynamic items with the same density but different sizes: item one is 100 x 100 points and item two is 100 x 200 points. In this example, item two has twice the effective mass of item one. In an elastic collision, these items exhibit a natural conservation of momentum according to their relative masses.
A 100 x 100 point dynamic item with a density of 1.0, to which you apply a force (via a push behavior) of magnitude 1.0, accelerates at 100 points per second².