k. stirewalt cse 335: software design synthetic oo design concepts & reuse lecture 8: modeling...

CSE 335: Software Design K. Stirewalt

Synthetic OO Design Concepts & Reuse Lecture 8: Modeling & documenting collaborations

Topics:– Synthesis of multiple collaborations– Documenting collaborations with abstract roles– A “model” of reuse in role-based designs


New conceptsCollaboration: Contextual relationship among

instances that interact to implement a desired functionality– pattern of message exchange among those instances to

achieve some goal– protocol

Role: that subset of an object’s characteristics needed to fulfill its responsibilities in a collaboration– alternatively, a “slot” that can be filled by objects that wish

to participate in the collaboration– such objects are said to “play” the role

Observe: Both definitions refer to instances

Goals:1. Design reusable collaborations2. Compose applications by synthesizing collaborations


Example

Suppose we want to design a graphical browser that allows users to view and print documents

Two collaborations here:1. A viewPort that displays lines of text, which it

receives by collaborating with a docMgr; and2. A printButton that sends messages to docMgr

to cause it to print.

Observe:– docMgr object is involved in both collaborations– It plays a different role in each


Graphical depiction of example app

#ifndef VIEWPORT_H#define VIEWPORT_H

#include <FL/Fl_Multiline#include “ViewPortModel.h

class ViewPort : public public: ViewPort( int x, int y, unsigned numberOfLines

Print

Note: The unseen document manager is serving lines from file “ViewPort.h”


Motivation: Explaining a designModern OO systems comprise lots of

collaborations

To understand such systems, requires visualizing: – the inter-connection of these objects (i.e.,

structure)– the dynamic interactions among these objects (i.e.,

behavior)

Problem: How can we visualize these phenomena in a useful way?


Sequence diagrams

Illustrate one instance of one collaboration among multiple objects

Feature:– Use of spatial position to reflect time dimension– Use of vertical bars to denote object “activity”– Graphic denotation of returns from operations

Note: Because it depicts only one instance, a single sequence diagram rarely sufficient to fully document a collaboration


Example sequence diagram

userEvent()buttonPressed(“Print”)

print : Button docMgr : MyDocManager

sd clickPrint

printDocument()


Example sequence diagram (continued)



sd clickPrint

printDocument()

activations





sd clickPrint

printDocument()

messages





sd clickPrint

printDocument()

return messages


New concept: Role

Defn: A “slot” that can be filled by many different object (or link) instances

Example: The ButtonListener “object” in a design that uses buttons– Not really any such thing as a ButtonListener

“object”– But lots of objects can be “plugged into” that slot.

Design tip: Identification of roles enables the design of reusable collaborations


Reusable interaction, defined using a role

userEvent()buttonPressed(…)

: Button listener : ButtonListener

sd clickButton


Instance of an abstract class?

userEvent()buttonPressed(…)

: Button listener : ButtonListener

sd clickButton

Notice: OK to depict what appears to be an “instance” of an abstract class in this situation


Collaboration diagram

listener : ButtonListener [0..*]button : Buttonlisteners

Button–ButtonListener

Example of a collaboration diagram.



listener : ButtonListener [0..*]button : Buttonlisteners

Button–ButtonListener


role role

role name type multiplicityrole name type

connector


Collaboration + seq diagramsA reusable collaboration is specified using:

– One collaboration diagram that names all of the roles and connectors and specifies any relevant multiplicities

– Multiple sequence diagrams, each depicting a “key” behavior among the objects that and links that play roles in the collaboration

Such documentation much more useful than “header” comments in the code


Another useful collaboration

Viewport–ViewPortModel


Recall the running example...

#ifndef VIEWPORT_H#define VIEWPORT_H

#include <FL/Fl_Multiline#include “ViewPortModel.h

class ViewPort : public public: ViewPort( int x, int y, unsigned numberOfLines

Print

Note: The unseen document manager is serving lines from file “ViewPort.h”


Exercise

Draw a sequence diagram that depicts the interaction between a viewport object (vp) and a DocumentManager object (docMgr) when vp is resized


Example: Class DocManagerclass DocManager {

public:

…

void printDocument() const;

unsigned docSize() const;

const string& docLine( unsigned ) const;

void insertLine( unsigned, const string& );

void appendLine( const string& );

void deleteLine( unsigned );

};


Example: Sequence diagram

docMgr : MyDocManagervp : ViewPortresize()

retrieve( 0, .... ) docSize()

docLine(0,...)

update()

retrieve( 1, .... )

docLine(1,...)

retrieve( n-1, .... )

docLine(n-1,...)

docSize()

docSize()

sd resizeView


Question

Consider the interaction between the document manager and a viewport that displays its contents. Are there any opportunities for role abstraction in this interaction?


When vp collaborates with a docMgr...

docMgr : MyDocManagervp : ViewPortresize()

retrieve( 0, .... ) docSize()

docLine(0,...)

update()

retrieve( 1, .... )

docLine(1,...)

retrieve( n-1, .... )

docLine(n-1,...)

docSize()

docSize()

sd resizeView


More general (reusable) interaction using the abstract role “model”

update()

retrieve(n) *

: ViewPort model : ViewPortModel

sd refreshView



vpm : ViewPortModelvp : ViewPortmodel

ViewPort–ViewPortModel



Reusable class ViewPortclass ViewPort : public Fl_Multiline_Output {

public:

ViewPort( int x, int y, int w, int h );

unsigned capacity() const;

void setModel( ViewPortModel* );

protected:

ViewPortModel* model;

void resize(int, int, int, int);

void update();

}; Question: Why is this method protected, rather than public?


ViewportModel interface

class ViewPortModel {

public:

virtual bool retrieve( unsigned lineNumber,

string& line ) const =0;

};


Example: ViewPort::Update methodvoid ViewPort::update(){ if (!model) return;

string contents, str;

const string endofline("\n");

for (int i=0; i < upperBound; i++) { if( model->retrieve(i, str) ) {

contents += str; contents += endofline; } }

value(contents.c_str());}


Example: Synthesis of multiple rolesclass MyDocManager : public DocManager,

public ButtonListener, public ViewPortModel {

public: void buttonPressed( const string& s ) { if(s == “print”) DocManager::printDocument(); }

bool retrieve( unsigned lineNo, string& line ) const

{ bool retVal = (lineNo < DocManager::docSize()); if (retVal) line = DocManager::docLine(lineNo); return retVal; }};


Configuration codeint main(void) { ContainerWindow myContainer(500,150); MyDocManager docMgr(...); Button printButton(200, 80, “Print"); ViewPort viewPort(0,0, 350, 120);

printButton.addListener(&docMgr); viewPort.setModel(&docMgr);

myContainer.end(); myContainer.show();

return Fl::run();}


Terminology

Collaboration: Contextual relationship among instances that interact to implement a desired functionality

Collaboration diagram: A diagram describing the structural relationship among the roles in a collaboration

Collaboration role: A “slot” for an object or link within a collaboration. It specifies the kind of object or link that may appear in an instance of the collaboration.


ScrollBar collaboration

userEvent()announceNewValue(n)

: ScrollBar listener : ValuatorListener

sd moveHandle


Exercise

Integrate a scrollbar object into our viewport–docManager collaboration. Draw a sequence diagram to illustrate what happens when the user drags the slider handle to a new position.

k. stirewalt cse 335: software design synthetic oo design concepts & reuse lecture 8: modeling...

Documents

stirewalt cse

software design motivation

design reusable collaborations

collaboration slide

design modern oo systems

lots of collaborations

docmgr object

rolebased designs slide