Class

CAReplicatorLayer

A layer that creates a specified number of copies of its sublayers (the source layer), each copy potentially having geometric, temporal, and color transformations applied to it.

Overview

You can use a CAReplicatorLayer object to build complex layouts based on a single source layer that is replicated with transformation rules that can affect the position, rotation color, and time.

The code in Listing 1 shows a simple example: a red square is added to a replicator layer with an instance count of 5. The position of each replicated instance is offset along the x axis so that it appears to the right of the previous instance. The blue and green color channels are offset so that their values reach 0 at the final instance.

Listing 1

Using a replicator layer

let replicatorLayer = CAReplicatorLayer()
     
let redSquare = CALayer()
redSquare.backgroundColor = NSColor.white.cgColor
redSquare.frame = CGRect(x: 0, y: 0, width: 100, height: 100)
     
let instanceCount = 5
     
replicatorLayer.instanceCount = instanceCount
replicatorLayer.instanceTransform = CATransform3DMakeTranslation(110, 0, 0)
     
let offsetStep = -1 / Float(instanceCount)
replicatorLayer.instanceBlueOffset = offsetStep
replicatorLayer.instanceGreenOffset = offsetStep
    
replicatorLayer.addSublayer(redSquare)

The result of the code above is a row of five squares, with colors graduating from white to red, as shown in Figure 1.

Figure 1

Replicator layer example

Replicator layer example

Replicator layers can be nested. The code in Listing 2 adds replicatorLayer to a second replicator layer that offsets the position of each instance vertically and subtracts from the red channel.

Listing 2

Nesting replicator layers

let outerReplicatorLayer = CAReplicatorLayer()

outerReplicatorLayer.addSublayer(replicatorLayer)

outerReplicatorLayer.instanceCount = instanceCount
outerReplicatorLayer.instanceTransform = CATransform3DMakeTranslation(0, 110, 0)
outerReplicatorLayer.instanceRedOffset = offsetStep

The result of adding the code in Listing 2 is to create a grid with the value of the red channel being reduced in the vertical direction, as shown in Figure 2.

Figure 2

Nested replicator layer example

Nested replicator layer example

Topics

Setting Instance Display Properties

var instanceCount: Int

The number of copies to create, including the source layers.

var instanceDelay: CFTimeInterval

Specifies the delay, in seconds, between replicated copies. Animatable.

var instanceTransform: CATransform3D

The transform matrix applied to the previous instance to produce the current instance. Animatable.

Modifying Instance Layer Geometry

var preservesDepth: Bool

Defines whether this layer flattens its sublayers into its plane.

Accessing Instance Color Values

var instanceColor: CGColor?

Defines the color used to multiply the source object. Animatable.

var instanceRedOffset: Float

Defines the offset added to the red component of the color for each replicated instance. Animatable.

var instanceGreenOffset: Float

Defines the offset added to the green component of the color for each replicated instance. Animatable.

var instanceBlueOffset: Float

Defines the offset added to the blue component of the color for each replicated instance. Animatable.

var instanceAlphaOffset: Float

Defines the offset added to the alpha component of the color for each replicated instance. Animatable.

Relationships

Inherits From

Conforms To

See Also

Advanced Layer Options

class CAScrollLayer

A layer that displays scrollable content larger than its own bounds.

class CATiledLayer

A layer that provides a way to asynchronously provide tiles of the layer's content, potentially cached at multiple levels of detail.

class CATransformLayer

CATransformLayer objects are used to create true 3D layer hierarchies, rather than the flattened hierarchy rendering model used by other CALayer classes.