API reference
API reference
Select your platform
No SDKs available
No versions available

SystemDAG Class

Modifiers: final
Manages the dependency graph of systems in the Spatial SDK.
SystemDAG (Directed Acyclic Graph) is responsible for:
  • Tracking system dependencies and their relationships
  • Ensuring proper execution order based on dependencies
  • Detecting and preventing dependency cycles
  • Organizing systems into priority groups for execution
Systems can specify dependencies using mustRunBefore and mustRunAfter relationships, which this class resolves into a valid execution order.

Signature

class SystemDAG

Constructors

SystemDAG ()
Signature 
constructor()
Returns

Functions

addSystem ( system , priorityGroup )
Adds a system to the dependency graph.
This method:
  • Checks for duplicate systems
  • Adds the system's dependencies to the graph
  • Applies any missing edges to the new system
  • Registers the system in the appropriate priority group
Signature 
fun addSystem(system: SystemBase, priorityGroup: PriorityGroup = PriorityGroup.NORMAL)
Parameters
system: SystemBase
The system instance to add
priorityGroup: PriorityGroup
The priority group to assign to the system (default: NORMAL)
Throws
IllegalArgumentException
If the system is already registered
findSystem ( clazz )
Finds a system in the dependency graph. Throws an exception if the system is not found.
Signature 
fun <T : SystemBase> findSystem(clazz: KClass<T>): T
Parameters
clazz: KClass
The class reference of the system to find
Returns
The system instance
Throws
Exception
If the system is not registered with the SystemManager
removeSystem ( clazz )
Removes a system from the dependency graph.
Signature 
fun <T : SystemBase> removeSystem(clazz: KClass<T>): Boolean
Parameters
clazz: KClass
The class reference of the system to remove
Returns
Boolean
True if the system was found and removed, false otherwise
removeSystem ()
Removes a system from the dependency graph using reified type parameter.
Signature 
inline fun <T : SystemBase> removeSystem(): Boolean
Returns
Boolean
True if the system was found and removed, false otherwise
setEarlySystems ( earlySystems )
Sets the list of early systems that run before all other systems.
Signature 
fun setEarlySystems(earlySystems: List<SystemBase>)
Parameters
earlySystems: List
The list of early systems
Throws
RuntimeException
If early systems have already been set
setLateSystems ( lateSystems )
Sets the list of late systems that run after all other systems.
Signature 
fun setLateSystems(lateSystems: List<SystemBase>)
Parameters
lateSystems: List
The list of late systems
Throws
RuntimeException
If late systems have already been set
topologicalSortWithCycleDetection ()
Performs a topological sort of the systems based on their dependencies.
This method:
  • Validates that all required dependencies are present
  • Detects and reports any dependency cycles
  • Ensures systems are ordered according to their priority groups
  • Ensures systems within each priority group respect their dependencies
Signature 
fun topologicalSortWithCycleDetection(): MutableList<SystemBase>
Returns
MutableList
A sorted list of systems in the order they should be executed
Throws
RuntimeException
If required dependencies are missing or if a cycle is detected
tryFindSystem ( clazz )
Attempts to find a system in the dependency graph.
Signature 
fun <T : SystemBase> tryFindSystem(clazz: KClass<T>): T?
Parameters
clazz: KClass
The class reference of the system to find
Returns
The system instance if found, null otherwise
Did you find this page helpful?
Nav Logo
Virtual reality / Meta Horizon
Virtual reality / Meta Horizon
Virtual reality / Meta Horizon
English (US)
© 2026 Meta