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URootStateObject_Nested Documentation

Overview

URootStateObject_Nested extends URootStateObject and implements IMasterState_TreeInterface. It allows the creation of nested state machines, where each root state can manage multiple child states. Key features:

• Maintains a map of internal states keyed by class.
• Supports initial internal states on entry.
• Provides Blueprint and C++ methods for dynamic state management.
• Fully compatible with recursive state transitions.

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AddState_Implementation

Description: Adds a new state object of the given class to the nested root state and registers it in the internal map.

Parameter	Type	Description
StateClass	TSubclassOf<UStateObject>	Class of the state object to add

Example:

UStateObject* NewState = MyNestedRoot->AddState(MyStateClass);

Behavior Summary:

• Validates the state class.
• Checks for duplicates in the internal state map.
• Creates a new state object using NewObject<UStateObject>().
• Initializes the state object (Init(this)).
• Adds it to m_InternalStateMap.
• Returns the created state object, or nullptr if invalid.

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GetStateObject_Implementation

Description: Retrieves a state object from the internal state map, optionally creating it if it does not exist.

Parameter	Type	Description
StateClass	TSubclassOf<UStateObject>	Class of the state object to retrieve
bCreateIfNotPresent	bool	If true, creates the state if it does not exist

Example:

UStateObject* State = MyNestedRoot->GetStateObject(MyStateClass, true);

Behavior Summary:

• Returns the state object if already present in m_InternalStateMap.
• If not present and bCreateIfNotPresent is true, calls AddState_Implementation to create it.
• Returns nullptr if the class is invalid or creation fails.

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AddInternalState (Override)

Description: Wrapper for adding internal states, calls AddState_Implementation to maintain consistent management of the internal state map.

Parameter	Type	Description
StateClass	TSubclassOf<UStateObject>	Class of the state object to add

Example:

UStateObject* InternalState = MyNestedRoot->AddInternalState(MyStateClass);

Behavior Summary:

• Delegates state creation to AddState_Implementation.
• Ensures all internal states are tracked in m_InternalStateMap.

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StateEntered_Implementation (Override)

Description: Handles the logic for entering the nested root state. Automatically attempts to enter the initial internal state, if defined.

Example:

MyNestedRoot->StateEntered();

Behavior Summary:

• Calls the base StateEntered_Implementation.
• Checks if m_InitialStateClass is valid.
• Attempts a state transition to the initial internal state using AttemptStateTransition.
• Logs all transitions for debugging.

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StateExited_Implementation (Override)

Description: Handles logic for exiting the nested root state. Caches the currently active internal state for potential reuse.

Example:

MyNestedRoot->StateExited();

Behavior Summary:

• Stores the current m_ActiveInternalState class in m_InitialStateClass.
• Calls base StateExited_Implementation.
• Ensures proper exit of all active internal states.

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Properties

Name	Type	Description
m_InitialStateClass	TSubclassOf<UStateObject>	The initial internal state to enter when this root state is entered
m_InternalStateMap	TMap<TSubclassOf<UStateObject>, TObjectPtr<UStateObject>>	Map of internal states keyed by class for quick access and management

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Use Cases

• Nested state machines for AI, game logic, or global systems.
• Persistent tracking of internal states in complex scenarios.
• Dynamic creation and management of states at runtime.
• Easily extendable for recursive or hierarchical state systems.

Summary

URootStateObject_Nested extends the master state concept with class-based state mapping and initial state management. It enables dynamic creation and lookup of internal states, providing a flexible solution for AI behavior trees, modular game logic, or other systems where states must be efficiently referenced and controlled programmatically.