PART I CHAPTER 16 CS116 SENEM KUMOVA METİN 1

Structures Structures : Aggregate data types built using elements of other types struct Time { int hour; int minute; }; Members of the same structure must have unique names Two different structures may contain members of the same name struct st1{ int n; }; struct st2{ float n; }; Each structure definition must end with a semicolon CS116 SENEM KUMOVA METİN2

Creating Objects from A Structure in C++ struct Time { int hour; int minute; }; /*1*/ Time timeObject; /*2*/ Time timeArray[ 10 ]; /*3*/ Time *timePtr1; timePtr1= &timeobject; /*4*/ Time *timePtr2; timePtr2=new Time; /*5*/ Time &timeRef= timeObject; CS116 SENEM KUMOVA METİN3

Accessing Members of Structures Member access operators: Dot operator (.) for structures and objects Arrow operator (->) for pointers Print member hour of timeObject: Time timeObject; Time & timeRef= timeObject; cout << timeObject.hour; cout << timeRef.hour; OR Time * timePtr; timePtr = &timeObject; cout hour; // timePtr->hour is the same as ( *timePtr ).hour CS116 SENEM KUMOVA METİN4

EXAMPLE: Structure #include using namespace std; struct Time { int hour; // 0-23 int minute; // 0-59 }; void print(const Time & ); int main() { Time dinnerTime; dinnerTime.hour = 18; dinnerTime.minute= 30; cout<<endl; print( dinnerTime ); } CS116 SENEM KUMOVA METİN5 void print( const Time &t ) { cout <<setfill(‘0’)<<setw(2) <<t.hour <<“:”<< setw(2) <<t.minute ; }

STRUCTURES : No Information Hiding struct Time { int hour; int minute; }; Time x; x.hour=23; x.minute =54; All members of the structure are accessible!! All members are public NO INFORMATION HIDING CS116 SENEM KUMOVA METİN6

CLASSES A class is a data type Model objects that have both attributes (data members) behaviors (member functions -methods) Have a body delineated with braces ({ and }) Class definitions terminate with a semicolon class Time { /* data members and methods */}; CS116 SENEM KUMOVA METİN7 class tag keyword

Creating objects from classes class Time { // data members and methods …… }; /*1*/ Time dinnertime; // Creates an object of type Time /*2*/ Time array[ 5 ]; // array of Time objects /*3*/ Time *pointer1; // pointer to a Time object pointer1=&dinnertime; /*4*/ Time *pointer2= new Time; // pointer to a Time object /*5*/ Time &dinnerTime = dinnertime; // reference to a Time object CS116 SENEM KUMOVA METİN8

Information Hiding in C++ In C ++ classes can limit the access to their members and methods The three types of access a class can grant are: public : this keyword can be used to expose data members and methods (make accessible wherever the program has access to an object of the class ) private : this keyword can be used to hide data members and methods (make accessible only to member methods of the class ) protected : Similar to private ( will study it later!!) CS116 SENEM KUMOVA METİN9

Class Declaration class Time { public: void setTime( int, int ); // sets hour,minute public: void print(); // prints time private: int hour; // 0 – 23 int minute; // 0 – 59 }; // Time class consists of public methods and private data members // A colon : follows the keywords private and public CS116 SENEM KUMOVA METİN10

const keyword class Time { public: void setTime( int, int); // sets hour,minute void print() const; // prints time private: int hour; // 0 – 23 int minute; // 0 – 59 }; /* The keyword const in methods “print” shows that unlike method SetTime, these methods do not change the value of any Time data member… */ CS116 SENEM KUMOVA METİN11

Member selector operator Access to any class member, whether data member or method, is supported by the member selector operator “.” and the class indirection operator “->” class Time { public: void setTime( int h, int m); // sets hour,minute void print() const; // prints time private: int hour; // 0 – 23 int minute; // 0 – 59 }; main() { Time noww; // declare an object from class Time noww.setTime (11,30); noww.minute =34; // IS it possible ????? } CS116 SENEM KUMOVA METİN12

Class Scope class C {public : void m(); // public scope private : char d; // private scope == class scope int f(); }; // If no public and private keywords are used then the members are default in private scope class D { int x; } ; equals to class D { private : int x; }; CS116 SENEM KUMOVA METİN13

Defining Class Methods 1. A method can be defined inside the class declaration. Such a definition is said to be “inline” 2. A method can be declared inside the class declaration but can be defined outside the class declaration CS116 SENEM KUMOVA METİN14

Defining Class Methods 1 class Person { public : void setAge (int n) { age = n; }; // inline definition int getAge() const {return age}; private: int age; }; CS116 SENEM KUMOVA METİN15

Defining Class Methods 2 class Person { public : void setAge (int n); // declares the method int getAge() const; private: int age; }; // definitions for methods void Person :: setAge(int n) { age = n; } int Person :: getAge() const { return age; } CS116 SENEM KUMOVA METİN16

Using Classes in a Program #include using namespace std; class Person {public : void setAge (int n) { age = n; }; int getAge() const {return age;}; private: int age;}; void main() { Person p; p.setAge(12); cout <<p.getAge()<<endl; // p.age=13; ??????? Person student [2]; student[0].setAge(12); student[1].setAge(15); for (int i=0; i<2;i++) cout<<student[i].getAge()<<endl;} CS116 SENEM KUMOVA METİN17

Initializing Class Objects: Constructors Method that initializes class members Same name as the class No return type Member variables can be initialized by the constructor or set afterwards CS116 SENEM KUMOVA METİN18

Constructors : inline definition class Person { public : Person() { age =0; name =“Unknown”; } void setAge (int n) { age =n }; int getAge() const { return age }; void getName() const { cout <<name<<endl; } private: int age; string name; }; void main() { Person p; cout <<p.getAge()<<endl; cout <<p.getName()<<endl; } CS116 SENEM KUMOVA METİN19

Constructors class Person { public : Person() ; void setAge (int n) { age =n }; int getAge() const { return age }; void getName() const { cout <<name<<endl; } private: int age; string name; }; Person ::Person() {age =0; name =“Unknown”; } void main() { Person p; cout <<p.getAge()<<endl; cout <<p.getName()<<endl; } CS116 SENEM KUMOVA METİN20

Constructors : Overloading class Person { public : Person() { age =0; name =“Unknown”; } // First Constructor Person( const string & n) { name =n; } // Second Constructor void setAge (int n) { age =n; }; int getAge() const { return age }; void getName() const { cout <<name<<endl; } private: int age; string name;}; void main() {Person q; // USING FIRST CONSTRUCTOR cout <<q.getAge()<<endl; cout<< q.getName()<<endl Person p(“David”); // USING SECOND CONSTRUCTOR cout <<p.getAge()<<endl; cout <<p.getName()<<endl; } CS116 SENEM KUMOVA METİN21

AN EXAMPLE FROM YOUR TEXT BOOK #include using namespace std; class GradeBook { private: string courseName; public : void setcourseName (string n) { courseName=n; } string getcourseName() { return courseName;} GradeBook(string name) { setcourseName(name);} void displayMessage(){ cout<<“Welcome”<<getcourseName(); } }; void main() { GradeBook book1(“CS116 Int. To Programming II”); cout <<book1.getcourseName()<<endl; } CS116 SENEM KUMOVA METİN22

AN EXAMPLE FROM YOUR TEXT BOOK //GradeBook.h #include using namespace std; class GradeBook { private: string courseName; public : void setcourseName (string n) { courseName=n; } string getcourseName() { return courseName;} GradeBook(string name) { setcourseName(name);} void displayMessage() { cout<<“Welcome”<<getcourseName(); } }; CS116 SENEM KUMOVA METİN23 #include #include “GradeBook.h” using namespace std; void main() { GradeBook book1(“CS116”); cout <<book1.getcourseName()<<endl; }