Instance Property


The estimated duration required for the spring system to be considered at rest.


var settlingDuration: CFTimeInterval { get }


The duration is evaluated for the current animation parameters and may not the same as the duration.

Listing 1 creates a spring animation with a duration of 2 seconds.

Listing 1

Creating a spring animation

let spring = CASpringAnimation()

spring.keyPath = "position.x"
spring.fromValue = 0
spring.toValue = 640
spring.damping = 5
spring.duration = 2

With a damping coefficient of 5, the settling duration is approximately 2.85 seconds: the animated layer bounces around the target position several times before settling. However, changing the damping property to 15 reduces the settling duration to just over 1 second: the animated layer quickly comes to a stop as it reaches the target position.

All of the spring animation's physical attributes: damping, initialVelocity, mass and stiffness, can affect the settling duration.

See Also

Configuring Physical Attributes

var damping: CGFloat

Defines how the spring’s motion should be damped due to the forces of friction.

var initialVelocity: CGFloat

The initial velocity of the object attached to the spring.

var mass: CGFloat

The mass of the object attached to the end of the spring.

var stiffness: CGFloat

The spring stiffness coefficient.