[Newbies] Login procedure

[Ron Teitelbaum]

The problem with not testing my code:

Engine>>start
	"start the engine"
	[self fuel notEmpty] whileTrue: [
		movement := self fuel burnFuelWith: self spark
	].
	self transmission addMovement: movement

Doesn't move until the gas runs out!  :) 

So how about:

Engine>>start
	"start the engine"
	self spark turnOnElectricity.
	self engageStarter.
	self car isKeyInOnPosition whileTrue: [
		self runEngine
	].

Engine>>runEngine
	"run engine and pass movement to car"
	self fuel notEmpty ifTrue: [
		movement := self fuel burnFuelWith: self spark
		self transmission addMovement: movement
	] ifFalse: [
		self flashAnnoyingGasGuageLight.
	].

Ok I realize I'm probably only amusing myself but just incase it helps
someone I thought I'd point out my mistake!

Happy coding!

Ron

> From: Ron Teitelbaum
> Sent: Tuesday, June 06, 2006 9:43 AM
> 
> Hi Marko,
> 
> How are things in Finland?  I hear it is nice there and there seems to be
> a
> bit of a marketing campaign to get Americans to visit.
> 
> Anyway let's get to your question.  There are a number of ways to pass
> variables around.  The least effective way is to call methods with a lot
> of
> parameters.  Usually when I see methods with lots of parameters there is a
> problem and the problem most likely is that the methods is implemented in
> the wrong class.
> 
> Consider for a moment an example (since you asked for code examples)
> 
> Object subclass: Car
> 
> Object subclass: Engine
> 
> Object subclass: Fuel
> 
> Object subclass: Spark
> 
> Now we all know that for engine it run it needs Fuel and Spark so we could
> model the car so that it has each
> 
> Car
> 	instanceVariables: 'engine fuel spark'
> 
> Then we have
> 
> Car>>start
> 	"Start the car"
> 	self engine startWithFuel: self fuel andSpark: self spark onCar:
> self
> 
> Engine>>startWithFuel: someFuel andSpark: someElectricity onCar: aCar
> 	"run the engine"
> 	[someFuel notEmpty] whileTrue: [
> 		movement := someFuel burnFuelWith: someElectricity
> 	].
> 	aCar addMovement: movement
> 
> Car>>addMovement: someMovement
> 	"handle the movement of the engine through a transmission"
> 	self transmission handleMovement: someMovement
> 
> Ok so now I'm just amusing myself and thinking of the car being in idle so
> not using the fuel to move at all, wasting gas and promoting global
> warming.
> 
> 
> Getting back to your question what would happen instead if we have the
> parameters modeled where they are needed.  Ask yourself does the car need
> gas and fuel or does the engine need it instead?
> 
> So
> 
> Car
> 	instanceVariables: 'engine'
> 
> Engine
> 	instanceVariables: 'fuel spark transmission car'
> 
> Now when we build the objects we get much less parameter passing.
> 
> Car>>start
> 	"start the car"
> 	self engine start
> 
> Engine>>start
> 	"start the engine"
> 	[self fuel notEmpty] whileTrue: [
> 		movement := self fuel burnFuelWith: self spark
> 	].
> 	self transmission addMovement: movement
> 
> Now this was a long answer to your question and you may be sitting there
> saying; "What does this have to do with databases and buttons"!
> 
> Well if you model your parameters in objects they don't need passing.
> 
> TestDatabase
> 	instanceVariables: 'dataSource user password myDBConnection'
> 
> Then your button's method #executeTest
> 
> TestDatabase>>executeTest
> 	self myDBConnection on: self dataSource logon: self user password:
> self password.
> 
> Where dataSource can have host and port and dbname ...
> 
> I hope this helps for specific examples you could try
> http://www.google.com/search?hl=en&q=mysql+squeak
> 
> If this doesn't make sense, feel free to ask questions.  Let me know how
> it
> goes!
> 
> Happy coding!
> 
> Ron Teitelbaum
> President / Principal Software Engineer
> US Medical Record Specialists
> Ron at USMedRec.com
> 
> 
> 
> > From: Marko Koivuniemi
> > Sent: Monday, June 05, 2006 4:14 PM
> >
> >
> > Greetings from Finland. I am very excited about Squeak and SmallTalk - I
> > have find myself trying and exploring new programming things and that
> > hasn't happen since days of Commodore 64.
> >
> > Now I am trying to build (with one partner) a program which uses MySQL.
> > I wonder what would be best way to do login screen and actual program.
> >
> > Now we have morphs in windows which has login and password fields and
> > button. At this time idea is that this startup screen test login
> > information and then sends user (or user id) to another screen.
> >
> > I tested various styles and this kind of test "works" with button.
> >
> > test := DatabaseTest new.
> > loginbutton := MyButtonMorph new send: #executeTest to: test";
> >    openInHand".
> >
> > But what would be the best way to send many variables or values with
> > button click. (I have couple TextFieldMorphs storing values)
> >
> > I have googled a lot - and most examples deals scriptable buttons. (And
> > that is something I am not familiar with - as a novice I must see code
> > and try different things and see what's happening...)
> >
> >
> > --
> > Marko
> > _______________________________________________
> > Beginners mailing list
> > Beginners at lists.squeakfoundation.org
> > http://lists.squeakfoundation.org/mailman/listinfo/beginners
> 
> _______________________________________________
> Beginners mailing list
> Beginners at lists.squeakfoundation.org
> http://lists.squeakfoundation.org/mailman/listinfo/beginners