State Machine Presentation1 61

The State Pattern

Thursday, March 18, 2010

The State Pattern
An Appalling Exploration


:)


Why we need it...


B. F. Skinner
(do not do what he did)


Skinner box
“Operant
Conditioning
Chamber”


FAIL


What you do depends
on your state


Blood
test


Not
Thing

Blood
test


Not
Thing

Blood
test

Thing


First
aid


Not
Thing

First
aid


Not
Thing

First
aid

Thing


Not
Thing

First
aid
Thing

Not
Thing
Blood
test
Thing


1. Repeatedly using same test
2. Answers to test are
predictable and repeated
3. Test concerns one’s own
internal matters


Time to get practical.


public class Creature
{
public function Creature()
{
trace(“Ecce Creature”);
}
}


1. Come to life


1. Come to life
2. Talk to us


1. Come to life
2. Talk to us
3. Move around


{

{
}

public function zap() {}

public function talk() {}


{
}

public function zap() {}

public function talk() {}

public function walk() {}
}


...
public function implant( b : Brain )
{
mybrain = b;
}
...


public function zap()
{
// IF DEAD, BECOME ALIVE
// IF ALIVE, BECOME DEAD
}

public function walk()
{

}

public function talk()
{

}

{
}

{
// IF DEAD, DO NOTHING
// IF ALIVE, DESCRIBE CANCER CURE
}

{

}


}

{
// IF ALIVE, DESCRIBE CANCER CURE
}

{
// IF ALIVE, WALK TO LAB
}


{
private var amIdead : Boolean;

{
amIdead = true;
}

{

}

{
if( amIdead )
{
amIdead = false;
}
else
{
amIdead = false;
}
}

{

amIdead = false;
}
}

{
if( amIdead )
{
// DO NOTHING -- I’M DEAD
}
else
{
trace(“Listen to this...”);
trace(“the secrets of eternity”);
}
}

}

{
if( amIdead )
{
}
else
{
trace(“I’ll go to my lab”);
trace(“and cure cancer”);
}
}
}

[clip: Igor drops Hans
Delbruck’s brain]


{
private var amIdead : Boolean;
private var doIHaveDelbruckBrain :
Boolean;

{
amIdead = true;
}

{

}

{
mybrain = b;
if( mybrain == DELBRUCK_BRAIN )
// how??
{
doIHaveDelbruckBrain = true;
}
else
{
doIHaveDelbruckBrain = false;
}
}

}

{
if( amIdead )
{
}
else
{
if( doIHaveDelbruckBrain )
{
trace(“the secrets of
eternity”);
}

else
{
if( doIHaveDelbruckBrain )
{
trace(“the secrets of
eternity”);
}
else
{
trace(“UNNNNNNNH”);
}
}


Recommended