Interface IStateMachine

Defines the contract for a state machine that manages transitions and access to states within a state-driven system.

Namespace: Fwt.Core.StateMachines
Assembly: fwt.core.dll
Syntax
public interface IStateMachine
Remarks

Implementations of this interface allow querying the current state, retrieving states by index or type, and switching between states, optionally with context. This interface is typically used in scenarios where behavior changes dynamically based on the current state, such as workflow engines, game logic, or protocol handlers. Thread safety and state persistence are implementation-specific and should be considered when using concrete state machine types.

Methods

GetState(int)

Retrieves the state at the specified index within the state collection.

Declaration
ISmState GetState(int stateIndex)
Parameters
Type Name Description
int stateIndex

The zero-based index of the state to retrieve. Must be greater than or equal to 0 and less than the total number of states.
Returns
Type Description
ISmState

The state at the specified index if it exists; otherwise, null.
Remarks

If the state collection is null or the specified index is out of range, the method returns null.

GetState(Type)

Retrieves the state instance associated with the specified type.

Declaration
ISmState GetState(Type type)
Parameters
Type Name Description
Type type

The type for which to retrieve the corresponding state. Cannot be null.
Returns
Type Description
ISmState

The state instance associated with the specified type, or null if no matching state is found.

GetState<TState>(Type)

Retrieves the state object of the specified type and attempts to cast it to the requested state interface.

Declaration
TState GetState<TState>(Type type) where TState : ISmState
Parameters
Type Name Description
Type type

The type of the state object to retrieve.
Returns
Type Description
TState

An instance of TState if the state object can be cast to the specified type; otherwise, the default value for TState.
Type Parameters
Name Description
TState

The state interface type to return. Must implement ISmState.

SwitchState(ISmState)

Transitions the state machine to the specified new state.

Declaration
void SwitchState(ISmState newState)
Parameters
Type Name Description
ISmState newState

The state to switch to. If newState is the same as the current state, no transition occurs. Can be null to clear the current state.
Remarks

This method prepares the current state to stop before switching, and prepares the new state to run after the transition. If the new state is null, the state machine will have no active state after the call.

SwitchState(int)

Transitions the state machine to the state at the specified index.

Declaration
ISmState SwitchState(int stateIndex)
Parameters
Type Name Description
int stateIndex

The zero-based index of the state to switch to. Must correspond to a valid state within the state machine.
Returns
Type Description
ISmState

The state object representing the new active state after the transition.

SwitchState<TState>()

Switches the state machine to the specified state type and returns the new state instance if successful.

Declaration
TState SwitchState<TState>() where TState : ISmState
Returns
Type Description
TState

An instance of TState representing the new state if the switch is successful; otherwise, the default value for TState.
Type Parameters
Name Description
TState

The type of state to switch to. Must implement ISmState.
Remarks

If the requested state type is not available or cannot be switched to, the method returns the default value for TState. This method is typically used to transition the state machine to a specific state and obtain a strongly-typed reference to it.

SwitchState<TState, TContext>(TState, TContext)

Transitions the state machine to the specified new state, providing the associated context for the state.

Declaration
void SwitchState<TState, TContext>(TState newState, TContext context) where TState : ISmStateWithContext<TContext>
Parameters
Type Name Description
TState newState

The state to transition to. If equal to the current state, no transition occurs.
TContext context

The context object to associate with the new state. This is set on the state before it is started.
Type Parameters
Name Description
TState

The type of the state to transition to. Must implement ISmStateWithContext<TContext>.
TContext

The type of the context object to be associated with the new state.
Remarks

If the current state is not null, it is prepared to stop before the transition. The new state's context is set before it is prepared to run. No action is taken if the new state is the same as the current state.

SwitchState<TState, TContext>(TContext)

Declaration
TState SwitchState<TState, TContext>(TContext context) where TState : ISmStateWithContext<TContext>
Parameters
Type Name Description
TContext context
Returns
Type Description
TState
Type Parameters
Name Description
TState
TContext

Tick()

Advances the state machine by invoking the tick operation on the current state, if one is set.

Declaration
void Tick()
Remarks

Call this method periodically to update the state machine's behavior. If no current state is assigned, this method has no effect.

Extension Methods