---
title: dependencies
framework: realitykit
role: symbol
role_heading: Type Property
path: realitykit/system/dependencies
---

# dependencies

An array of dependencies for this system.

## Declaration

```swift
static var dependencies: [SystemDependency] { get }
```

## Mentioned in

Implementing systems for entities in a scene

## Discussion

Discussion If you need to specify the update order between your system and other systems in your app, you can do that using this property. If your system has no dependencies, you don’t need to declare this property. RealityKit provides a default implementation for systems with no dependencies. Here’s an example where one other system updates before this system, and another system updates after it. class SystemB : RealityKit.System {     static var dependencies: [SystemDependency] {         [.after(SystemA.self),        // Run SystemB after SystemA.          .before(SystemC.self)]       // Run SystemB before SystemC.      }     // ... } When the app runs, RealityKit calls update(context:) on SystemA first, then on SystemB, and then on SystemC.

## See Also

### Specifying dependencies

- [SystemDependency](realitykit/systemdependency.md)