1

Software Design UML Basics Template Class Example (Chain) STL Vector Class Operator Overloading Ray class Example

CSE 30331CSE 30331Lecture 2 – Design & Some ExamplesLecture 2 – Design & Some Examples

2

Software Design Overview State the problem to be solved.

Analyze the problem to extract requirements. Proceed through a series of stages to produce a product

that is reliable and easy to maintain.

3

Software Design Overview

Prior to the standardization of the software development life cycle: Programmers added code to software with little

attention to its integration into the system. Over time systems deteriorated and became so

difficult to update that programmers had to develop new software to replace them.

4

Software Design Stages

Request Analysis Design Implementation Testing Maintenance

5

Software Design Stages

Request Client has problem software might solve Consultant undertakes a feasibility study for the project

Analysis Identifes system requirements Creates a functional specification Lists needs and special requirements

6

Software Design Stages

Design Translates the functional specification into an abstract

model of the system Identifies the components of the system Develops algorithms for implementation

Implementation Uses a programming language Uses the design specification Creates code for all system components

7

Software Design Stages

Testing Unit testing & Integration testing Verification – meets requirements Validation – meets user’s needs Syntax vs. Semantic (logical) errors Black-box vs. White-box testing Test data (inputs in range, out of range, boundary)

Maintenance Periodically update the software to stay current and to

respond to changing needs of the client.

8

UML – Unified Modeling Language

Common representation of program … Design Usage Components

Use Case Diagrams Class Diagrams

9

UML – Use Case Diagrams

Represent from user perspective how program (system) is to be used

ATM example Make deposit Make withdrawal Check account balance Transfer funds between accounts

Make deposit

Make withdrawal

Check Account Balance

Transfer funds between accounts

10

UML – Class Diagrams

Represent attributes and behavior of class Top box shows data members Bottom box shows member functions “+” indicates public “-” indicates private

Account Class Example

accountNumber : integerpin : integeravailableBalance : doubletotalBalance : double

validatePin( ) : booleangetAvailableBalance( ) : doublegetTotalBalance( ) : doublecredit( )debit( )

11

UML – Class Relationships

Diamond indicates composition relationship ATM has-a Screen ATM has-a Keypad ATM has-a CashDispenser ATM has-a DepositSlot

Screen

ATM

Keypad

CashDispenserDepositSlot

1

111

1

1

11

12

UML – System Model

Shows class relationships AND interactions

Screen

ATM

bankDatabase

DepositSlot

1

1

0..1

1

1

11

CashDispenser

WithdrawalExecutes

1

1 1

0..1

Accesses/Modifies account balance through

Authenticates user against

13

Operator Overloading

Operators may be overloaded as either … Member functions

Left operand must be object of this class (rhs + lhs) Friend functions

At least one operand is member of this class Function has access to private parts of class

Free functions Function has no access to private parts of class Class must provide all necessary public methods

14

Operator Overloading Example

Ray class (2-d vectors in Cartesian coords) Data Members

dx & dy – specify direction and magnitude Member Functions

Ray(x,y) – constructor operator+(r) – vector addition operator*(s) – scalar multiplication (r*s)

Friend functions Operator<<(str,r) – insertion into stream Operator>>(str,r) – extraction from stream Operator*(s,r) – scalar multiplication s*r

15

Ray Class#include <iostream>class Ray{ friend Ray operator*(double s, Ray r); friend std::istream& operator>> (std::istream& str, Ray& r); friend std::ostream& operator<< (std::ostream& str, Ray r); public: Ray(const double x=1.0, const double y=0.0); Ray operator*(double s); Ray operator+(Ray r);

private: double dx, dy;};

16

Ray Class Member Functions#include “Ray.h”

Ray::Ray(const double x, const double y): dx(x), dy(y){ }Ray Ray::operator*(double s){ // multiply both components by scalar s Ray result(s*dx, s*dy); return result;}Ray Ray::operator+(Ray r){ // add corresponding components of two rays

Ray result(dx+r.dx, dy+r.dy);return result;

}

17

Ray Class Friend FunctionsRay operator*(double s, Ray r){// multiply both components by scalar s Ray result(s*r.dx, s*r.dy); return result;}std::istream& operator>> (std::istream& str, Ray& r){ //extract two ray components str >> r.dx >> r.dy; return str;}std::ostream& operator<< (std::ostream& str, Ray r){ // insert two ray components separated by a space str << r.dx << “ “ << r.dy; return str;}

18

Ray Class – sample use

// declare Rays and exercize all related operators#include <iostream>#include “Ray.h”using namespace std;int main( ){ Ray r1, r2, result; cout << “Enter two rays x1 y1 x2 y2: “; cin >> r1 >> r2; result = -1.0 * ((r1 + r2) * 4.0); cout << “r1 = “ << r1 << “, r2 = “ << r2 << endl; cout << “-1.0 * ((r1 + r2) * 4.0) = “ << result << endl; return 0;}

19

Template Class Example

Chain class (sequence of items) Data member

STL vector of items Member functions

Chain( ) – creates empty sequence Append (item) – appends item to sequence Total ( ) – traverses sequence and totals it

NOTE: “total” has different meanings depending on what “+” means with respect to the item type Strings are concatenated Rays are added as 2-d vectors in Cartesian coordinates ints are added normally

20

Chain Class

template<class T>

class Chain

{

public:

Chain();

void append(const T& item);

T total();

private:

vector<T> items;

};

21

Chain Class Members

// simple constructor, nothing to dotemplate<class T>Chain<T>::Chain(){ }

// simple append, just use vector push_back to do alltemplate<class T>void Chain<T>::append(const T& item){ items.push_back(item);}

22

Chain Class Members// pretty simple total procedure: handle empty Chain// in some way, then sum, concatenate, or whatever// is appropriate for “+” with respect to items of // type Ttemplate<class T>T Chain<T>::total(){ if (0 == items.size()) return T(); // or throw an emptyChain error

T result(items[0]); // start with value of first item for (int i=1; i<items.size(); i++) result = result + items[i]; // “sum” each other item return result;}

23

Chain of Rays Example#include <iostream>#include “Ray.h”#include “Chain.h”using namespace std;int main( ) { Ray r; Chain<Ray> sequence; cout << “Enter a ray -- x y (\"e\" to end): “; while (cin >> r) { sequence.append(r); cout << “Enter a ray -- x y (\"e\" to end): “; } cout << “TOTAL is : “ << sequence.total() << endl; return 0;}

24

Chain of strings Example#include <iostream>#include <string>#include “Chain.h”using namespace std;int main( ) { string str; Chain<string> sequence; cout << “Enter a name : “; while (getline(cin,str) && (str != “”)) { sequence.append(str); cout << “Enter a name : “; } cout << “TOTAL is : “ << sequence.total() << endl; return 0;}

25

STL Containers

All containers have the following ContType c – create empty container ContType c1(c2) – create copy of container ContType c(beg,end) – initialize with items[beg,end) c.~ContType() – delete elements and free memory c.size() – return number of elements c.empty() – is container empty or not c.max_size() – max number of elements possible

26

STL Containers

All containers have the following c1 == c2 – are containers equal? c1 != c2 – are they not equal c1 < c2 – less than based on lexicographical ordering c1 > c2 – greater than c1 <= c2 – less than or equal c1 >= c2 – greater than or equal c1 = c2 – assigns elements of c2 to c1 c1.swap(c2) – swaps elements of two containers swap(c1,c2) – same as above

27

STL Containers

All containers have the following c.begin() – returns iterator to first element c.end() – returns iterator past last element c.rbegin() – returns reverse iterator for last element c.rend() – returns reverse iterator before first element c.insert(pos,elem) – inserts copy of elem c.erase(beg,end) – removes elements [beg,end) c.clear() – removes all elements c.get_allocator() – returns memory model

28

Vector Container

Vectors also have … vector<T> c – creates empty vector vector<T> c1(c2) – creates copy of vector c2 vector<T> c(n) – creates vector of n elements vector<T> c(n,e) – creates vector of n copies of e vector<T> c(beg,end) – creates vector copying

elements from range [beg,end) c.~vector<T>() – clears elements and frees memory

29

Vector Container

Vectors also have … c.capacity() – returns max elements w/o reallocation c.reserve(n) – enlarges capacity c.assign(n,e) – assigns n copies of e c.assign(beg,end) – assigns elements [beg,end) c.at(idx) – returns element at position idx c[idx] – same as previous c.front() – returns first element c.back() – returns last element

30

Vector Container

Vectors also have … c.insert(pos,n,e) – inserts n copies of e at iterator pos c.insert(pos,beg,end) – inserts at iterator pos the

elements in range [beg,end) c.push_back(e) – appends e to vector c.pop_back() – removes last element from vector c.erase(pos) – removes element at iterator pos c.resize(num) – changes number of elements and fills

with value of default element constructor c.resize(num,e) – changes size and fills with e