# draw(_:in:) Tells the delegate to implement the display process using the layer’s context. ``` optional func draw(_ layer: CALayer, in ctx: CGContext) ``` ## Parameters `layer` The layer whose contents need to be drawn. `ctx` The graphics context to use for drawing. The graphics context incorporates the appropriate scale factor for drawing to the target screen. ## Discussion The [`draw(_:in:)`](/documentation/QuartzCore/CALayerDelegate/draw(_:in:)) method is called when the layer is marked for its content to be reloaded, typically with the [`setNeedsDisplay()`](/documentation/QuartzCore/CALayer/setNeedsDisplay()) method. It is not called if the delegate implements the [`display(_:)`](/documentation/QuartzCore/CALayerDelegate/display(_:)) method. You can use the context to draw vectors, such as curves and lines, or images with the method. The following code shows how you can create a class named `LayerDelegate` that implements [`CALayerDelegate`](/documentation/QuartzCore/CALayerDelegate) and sets it as a layer’s (named `sublayer`) delegate. When [`setNeedsDisplay()`](/documentation/QuartzCore/CALayer/setNeedsDisplay()) is called on `sublayer`, the delegate’s [`draw(_:in:)`](/documentation/QuartzCore/CALayerDelegate/draw(_:in:)) method draws an ellipse fitting the bounding box of the layer using the function. ```swift let delegate = LayerDelegate() lazy var sublayer: CALayer = { let layer = CALayer() layer.delegate = self.delegate return layer }() // sublayer.setNeedsDisplay() class LayerDelegate: NSObject, CALayerDelegate { func draw(_ layer: CALayer, in ctx: CGContext) { ctx.addEllipse(in: ctx.boundingBoxOfClipPath) ctx.strokePath() } } ``` > Important: > This method is not called if the delegate implements ``doc://com.apple.quartzcore/documentation/QuartzCore/CALayerDelegate/display(_:)``. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)