EMERGENT DESIGNVarokas Panusuwan

DESIGN PATTERNWhat is it?

PATTERNS

Scott BainThe Pattern is in the problem

Dont solve the problem, discover the problem.

Christopher Alexander, ArchitectDesign: the process of inventing things which display new physical order, organization, form, in response to function.

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DESIGN PATTERNLanguage for designNoobs vs Pro talks

COMMONALITYVARIABILITYANALYSIS

5 Each

Browser: "As a URLReader, I can read HTML either from File location (file:///) or over internet (http://)"

Browser: "As a Renderer, I want to show image as "loading..." until the image is loaded

PROGRAMMING BY INTENTIONGoogle Example

PATTERNS DISCOVERY PRACTICESDont worry about creational pattern yet.

ECHO HELLO WORLDA program read input from keyboard or scannerA program sends the output to either printer or screen

DOMElement are the things that can be shown on screenelement can contain each otherA browser can call render() and the element should render itself and everything inside

SWING BORDERComponent can have bordersBorders can be stacked on top of each otherMany kinds of borderImage borderPlain borderDotted borderWhen render() the component draw itself and the border

ENCRYPTIONAn encryption module can encrypt a plain string to encrypted stringMany standards : DES, AES, BlowfishSome encryption standards are composite of others e.g. 3 DES = DES(DES(DES(text)))DESAES = DES(AES(text))

500 100 50 20 10

CREATIONAL PATTERNSWhat can exist in the world?

FACTORYFew possible configurationDefined statically in code

BUILDERMany possible configurationSome rules coded inUse in runtime to set up other objects

DESIGN TOOLSCVARedundancyCouplingEncapsulation

COUPLINGAccidentalIntentional

ENCAPSULATIONswitch (input) { case A : doAlgoA(); case B : doAlgoB();}AlgoProgram

AlgoAAlgoB

LEVELSConceptualSpecificationImplementationhttp://www.syntropy.co.uk/papers/modelingwithpurpose.pdf

UNFIT PATTERNSHandlersDecorators

EMERGENT DESIGNAt LastWhat is it?

StarbucksCreate a software for cashier and baristaA program accepts order from user (cashier as them)example:What kind of coffeeWhat size etcA program compute cost based on the orderA program shows the barista what to doexample:Put in 2x coffeePut in milkput in iceshakedone

Starbucks (v1)

Select Size of cup (S,M,L)put coffee(S) Cup -> Coffee(M) Cup -> Coffee x 2(L) Cup -> Coffee x 3

Starbucks (v2) Select Coffee Type (Hot/Cold)Select Size of cup (S,M,L)Make CoffeeHot :: Cup -> Coffee (S,M,L)Cold :: Cup -> Coffee (S,M,L) -> Ice (always x 1)-- redraw this(keep v1) --

Starbucks (v3)Select Coffee Type (Hot/Cold)AmericanoEspressoLatte Select Size (S,M,L)Make CoffeeCoffee Americano = Coffee + WaterLatte = Coffee + MilkEspresso = Coffee + (nothing)Hot :: Cup-> Coffee (S,M,L) Cold :: Cup -> Coffee (S,M,L) -> Ice (always x 1)-- redraw this (keep v1&v2) --

`What is the differences between requirement and design?