ml::StateManager< StateEnum > Class Template Reference

Single-enum state machine with enter/exit callbacks. More...

#include <StateManager.h>

Public Member Functions
	StateManager ()=default
	Default constructor — initial state is the zero-value of StateEnum.
template<typename T = StateEnum>
	StateManager (std::enable_if_t<!std::is_void_v< T >, T > initialState)
	Construct with an explicit initial state.
template<typename T = StateEnum>
std::enable_if_t<!std::is_void_v< T >, T >	getState () const
	Return the current state value.
template<typename T = StateEnum>
std::enable_if_t<!std::is_void_v< T >, bool >	isState (T state) const
	Return true if currently in state.
template<typename T = StateEnum>
std::enable_if_t<!std::is_void_v< T > >	onStateEnter (std::function< void(T)> callback)
	Register a callback invoked after each state transition.
template<typename T = StateEnum>
std::enable_if_t<!std::is_void_v< T > >	onStateExit (std::function< void(T)> callback)
	Register a callback invoked before each state transition.
template<typename T = StateEnum>
std::enable_if_t<!std::is_void_v< T > >	setState (T newState)
	Transition to a new state.

Detailed Description

template<typename StateEnum = void>
class ml::StateManager< StateEnum >

Single-enum state machine with enter/exit callbacks.

StateManager<StateEnum> stores one active state value and fires optional callbacks on every transition. It is used in two places:

• Customizable<Manifest> inherits StateManager<Manifest::State> to give traits their own state machine.
• MultiCustomStateManager uses SingleStateManager (a similar type) to aggregate multiple state machines for components.

All methods are guarded by std::enable_if so they exist only when StateEnum is not void. The void specialization at the bottom of this file is a no-op that compiles cleanly when the manifest declares no State enum.

Usage

struct MyManifest {
    enum class State { Idle, Running, Paused };
};
 
class MyComponent : public ml::ComponentWith<MyManifest> {};
 
MyComponent c;
 
c.onStateEnter([](MyManifest::State s){
    if (s == MyManifest::State::Running) startAnimation();
});
 
c.onStateExit([](MyManifest::State s){
    if (s == MyManifest::State::Running) stopAnimation();
});
 
c.setState(MyManifest::State::Running); // fires exit(Idle), then enter(Running)
c.isState(MyManifest::State::Running);  // true
c.getState();                           // MyManifest::State::Running

Template Parameters

StateEnum

An enum class type representing the possible states. Defaults to void (selects the no-op specialization).

See also

Customizable, MultiCustomStateManager, GatherStates

StateManager.

Definition at line 84 of file StateManager.h.

Constructor & Destructor Documentation

StateManager() [1/2]

template<typename StateEnum = void>

template<typename T = StateEnum>

ml::StateManager< StateEnum >::StateManager ( std::enable_if_t<!std::is_void_v< T >, T > initialState )

explicit

Construct with an explicit initial state.

Parameters

initialState

The state to start in. The enter callback is not fired during construction.

StateManager() [2/2]

template<typename StateEnum = void>

ml::StateManager< StateEnum >::StateManager ( )

default

Default constructor — initial state is the zero-value of StateEnum.

Member Function Documentation

getState()

template<typename StateEnum = void>

template<typename T = StateEnum>

std::enable_if_t<!std::is_void_v< T >, T > ml::StateManager< StateEnum >::getState

(

)

const

Return the current state value.

Returns

The active StateEnum value.

isState()

template<typename StateEnum = void>

template<typename T = StateEnum>

std::enable_if_t<!std::is_void_v< T >, bool > ml::StateManager< StateEnum >::isState

(

T

state

)

const

Return true if currently in state.

Parameters

state

The state value to compare against.

Returns

true if the current state equals state.

onStateEnter()

template<typename StateEnum = void>

template<typename T = StateEnum>

std::enable_if_t<!std::is_void_v< T > > ml::StateManager< StateEnum >::onStateEnter

(

std::function< void(T)>

callback

)

Register a callback invoked after each state transition.

The callback receives the newly entered state. Only one enter callback is active at a time; calling this again replaces it.

Parameters

callback

Function called with the new state after each transition.

onStateExit()

template<typename StateEnum = void>

template<typename T = StateEnum>

std::enable_if_t<!std::is_void_v< T > > ml::StateManager< StateEnum >::onStateExit

(

std::function< void(T)>

callback

)

Register a callback invoked before each state transition.

The callback receives the state being left. Only one exit callback is active at a time; calling this again replaces it.

Parameters

callback

Function called with the old state before each transition.

setState()

template<typename StateEnum = void>

template<typename T = StateEnum>

std::enable_if_t<!std::is_void_v< T > > ml::StateManager< StateEnum >::setState

(

T

newState

)

Transition to a new state.

Fires the exit callback with the current state, updates the stored state to newState, then fires the enter callback with the new state. Either callback may be unset (nullptr), in which case it is skipped.

Parameters

newState

The state to transition into.

---

The documentation for this class was generated from the following file:

• Resources/StateManager.h