Destructor http://ecomputernotes.com

Review Copy constructors Destructor Accessor Functions this Pointer http://ecomputernotes.com

this Pointer There are situations where designer wants to return reference to current object from a function In such cases reference is taken from this pointer like (*this) http://ecomputernotes.com

Example Student Student::setRollNo(int aNo) { … return *this; } Student Student::setName(char *aName) { … return *this; } http://ecomputernotes.com

Example int main() { Student aStudent; Student bStudent; bStudent = aStudent.setName(“Ahmad”); … bStudent = aStudent.setName(“Ali”).setRollNo(2); return 0; } http://ecomputernotes.com

Separation of interface and implementation Public member function exposed by a class is called interface Separation of implementation from the interface is good software engineering http://ecomputernotes.com

Complex Number There are two representations of complex number Euler form z = x + i y Phasor form z = |z| (cos  + i sin ) z is known as the complex modulus and  is known as the complex argument or phase

Example

Example class Complex{ //old float x; float y; public: void setNumber(float i, float j){ x = i; y = j; } … }; http://ecomputernotes.com

Example class Complex{ //new float z; float theta; public: void setNumber(float i, float j){ theta = arctan(j/i); … } … }; http://ecomputernotes.com

Advantages User is only concerned about ways of accessing data (interface) User has no concern about the internal representation and implementation of the class http://ecomputernotes.com

Separation of interface and implementation Usually functions are defined in implementation files (.cpp) while the class definition is given in header file (.h) Some authors also consider this as separation of interface and implementation http://ecomputernotes.com

Student.h class Student{ int rollNo; public: void setRollNo(int aRollNo); int getRollNo(); … }; http://ecomputernotes.com

Student.cpp #include “student.h” void Student::setRollNo(int aNo){ … } int Student::getRollNo(){ … } http://ecomputernotes.com

Driver.cpp #include “student.h” int main(){ Student aStudent; } http://ecomputernotes.com

There are functions that are meant to be read only There must exist a mechanism to detect error if such functions accidentally change the data member const Member Functions http://ecomputernotes.com

Keyword const is placed at the end of the parameter list const Member Functions http://ecomputernotes.com

const Member Functions Declaration: class ClassName{ ReturnVal Function() const; }; Definition: ReturnVal ClassName::Function() const{ … } http://ecomputernotes.com

Example class Student{ public: int getRollNo() const { return rollNo; } }; http://ecomputernotes.com

const Functions Constant member functions cannot modify the state of any object They are just “read-only” Errors due to typing are also caught at compile time http://ecomputernotes.com

Example bool Student::isRollNo(int aNo){ if(rollNo = = aNo){ return true; } return false; } http://ecomputernotes.com

Example bool Student::isRollNo(int aNo){ /*undetected typing mistake*/ if(rollNo = aNo){ return true; } return false; } http://ecomputernotes.com

Example bool Student::isRollNo (int aNo)const{ /*compiler error*/ if(rollNo = aNo){ return true; } return false; } http://ecomputernotes.com

const Functions Constructors and Destructors cannot be const Constructor and destructor are used to modify the object to a well defined state http://ecomputernotes.com

Example class Time{ public: Time() const {} //error… ~Time() const {} //error… }; http://ecomputernotes.com

const Function Constant member function cannot change data member Constant member function cannot access non-constant member functions http://ecomputernotes.com

Example class Student{ char * name; public: char *getName(); void setName(char * aName); int ConstFunc() const{ name = getName(); //error setName(“Ahmad”);//error } }; http://ecomputernotes.com

this Pointer and const Member Function this pointer is passed as constant pointer to const data in case of constant member functions const Student *const this; instead of Student * const this; http://ecomputernotes.com