---
title: emitterCells
framework: quartzcore
role: symbol
role_heading: Instance Property
path: quartzcore/caemittercell/emittercells
---

# emitterCells

An optional array containing the sub-cells of this cell.

## Declaration

```swift
var emitterCells: [CAEmitterCell]? { get set }
```

## Discussion

Discussion When specified, each particle emitted by the cell acts as an emitter for each of the cell’s sub-cells. The emission point is the current particle position and the emission angle is relative to the current direction of the particle. The default value of this property is nil. The following code shows how you can create a firework style effect using sub-cells. The fireworkCell has an emission longitude of one quarter turn anti-clockwise to emit particles upwards. It emits trailCell instances which have a slight yAcceleration that simulates gravity. Note that the scale and color of fireworkCell are inherited by trailCell. Listing 1. Creating particle trails let image = UIImage(named: "RadialGradient.png")!.cgImage      let emitterLayer = CAEmitterLayer()      emitterLayer.emitterPosition = CGPoint(x: 512, y: 512)      let fireworkCell = CAEmitterCell() fireworkCell.color = UIColor.red.cgColor fireworkCell.birthRate = 3 fireworkCell.lifetime = 10 fireworkCell.velocity = 100 fireworkCell.scale = 0.05 fireworkCell.emissionLongitude = -CGFloat.pi * 0.5 fireworkCell.emissionRange = -CGFloat.pi * 0.25 fireworkCell.contents = image      let trailCell = CAEmitterCell() trailCell.yAcceleration = 20 trailCell.birthRate = 10 trailCell.lifetime = 3 trailCell.contents = image      fireworkCell.emitterCells = [trailCell] emitterLayer.emitterCells = [fireworkCell]      view.layer.addSublayer(emitterLayer)

## See Also

### Providing Emitter Cell Content

- [contents](quartzcore/caemittercell/contents.md)
- [contentsRect](quartzcore/caemittercell/contentsrect.md)