SDDKit - State Driven Development Kit

Easiest way for implementing Hierarchical State Machine (HSM) based programs in Objective-C.

Installation

Clone or download source codes directly, or by using CocoaPods.

pod 'SDDKit'

High Level Aspects

Classes listed below gives the major functionalities of SDDKit.

SDDState
SDDStateMachine
SDDEventsPool
SDDBuilder

But as being a 'Client', two of them need to be cared about for you.

SDDEventsPool
SDDBuilder

SDDState

SDDState contains activation and deactivation blocks, which performs the entering and exiting actions.

SDDStateMachine

Every instance of SDDStateMachine represents a standalone statemachine object. Each of them describes state hierarchies and transitions.

SDDEventsPool

The event dispatching class. It is important to know that a statemachine have to be added as a subscriber of eventspool before it can drive by incoming events. Some apps have more than one eventspool to avoid duplication of signal names.

SDDBuilder

A string parsing based SDDStateMachine builder. It provides the easiest way for generating and organizing multiple statemachines.

Examples

Simple

SDDBuilder *builder = [[SDDBuilder alloc] initWithLogger:nil epool:[SDDEventsPool sharedPool]];

[builder addStateMachineWithContext:nil dsl:SDDOCLanguage(
	// Every statemachine can and must have one topstate
	[TopState
		// Two substates
		[A]
		[B]
	]

	// Since TopState has two descendants, a $Default transition have to be provided to avoid ambiguity.
	// Another choice is using $Initial transition from outter state [.] such as:
	// [.] -> [A]: $Initial
	[TopState] -> [A]: $Default
	
	// If [A] is the current state and signal 'E1' occurs, it will transit to state [B]
	[A]->[B]: E1
)];

[[SDDEventsPool sharedPool] scheduleEvent:SDDLiteral(E1)];
// Now we are in state [B]

Activation and Deactivation

A statemachine with nil context helps nothing. Something has to be done that we could distinguish between one state and another. That's the reason why we are using statemachine, aren't we?

@interface Charles
@end

@implementation Charles
- (void)wakeup {
	NSLog(@"Good morning.")
}

- (void)sayGoodbye {
	NSLog(@"Bye, see ya.");
}

- (void)goToBed {
	NSLog(@"Good night.")
}

@end

int main() {
	Charles *charles = [[Charles alloc] init];

	SDDBuilder *builder = [[SDDBuilder alloc] initWithLogger:nil epool:[SDDEventsPool sharedPool]];

	[builder addStateMachineWithContext:charles dsl:SDDOCLanguage(
		[Me
			[Awake  
				e: wakeup	  // 'e' is short for entering
				x: sayGoodbye // 'x' is short for exiting
			]
			[Asleep e: goToBed]
		]
	
		[.]      -> [Awake]  : $Initial
		[Awake]  -> [Asleep] : Sunset
		[Asleep] -> [Awake]  : Sunrise
	)];
	// Outputs 'Good morning.' for entering initial state [Awake]
	
	[[SDDEventsPool sharedPool] scheduleEvent:SDDLiteral(Sunset)];
	// Outputs 'Bye, see ya.' for exiting state [Awake]
	// Outputs 'Good night' for entering state [Asleep]
	
	[[SDDEventsPool sharedPool] scheduleEvent:SDDLiteral(Sunrise)];
	// Outputs 'Good morning.' for entering state [Awake]

	return 0;
}

charleslyh/SDDKit