Arrow Operator

Posted on April 1, 2023 • 3 minutes • 449 words

We can create a pointer variable for Complex data types such as struct and class. Also we can create a pointer for class and struct in stack and heap As similar as primitive data types.

Syntax

className *pointerName;
pointerName = &classObjectName;

Example

struct Student
{
    int mark;
    std::string name;
};

int main(int argc, char const *argv[])
{
    Student s;
    s.mark = 10;
    s.name = "ANOOP";

    Student *sPtr = &s;
}

Accessing data members using pointer:

We can access data members of a struct/class pointer variable by using * operator with .operator

Syntax

(*pointerName).memberVariableName

Example

int main(int argc, char const *argv[])
{
    Student s;
    s.mark = 10;
    s.name = "ANOOP";

    Student *sPtr = &s;
    std::cout << (*sPtr).mark << "," << (*sPtr).name << std::endl;
}

When it comes to structure and classes, we need to use * (star) and . (dot) operators in combination.

As a result, C++ introduced a new operator called -> (arrow-operator) to access class and structure members.

Syntax

pointerName->memberVariableName

Example

int main(int argc, char const *argv[])
{
    Student s;
    s.mark = 10;
    s.name = "ANOOP";

    Student *sPtr = &s;
    std::cout << sPtr->mark << "," << sPtr->name << std::endl;
}

new Operator for Constructors.

We also can use new operator for Parameterized constructors.

Syntax

ClassName *pointerName = new ClassName(arguments);

Example

#include<iostream>

class Rectangle
{
public:
    Rectangle(int len,int wid)
    {
        length = len;
        width = wid;
    }
    int getArea()
    {
        return length * width;
    }
    int length,width;
};

int main(int argc, char const *argv[])
{
    Rectangle *rPtr = new Rectangle(20,30);
    std::cout << "Area 2 : " << rPtr->getArea() << std::endl;
    delete rPtr;
}

Full Example

#include<iostream>

struct Student
{
    int mark;
    std::string name;
};

void myFunc1()
{
    Student s;
    s.mark = 10;
    s.name = "ANOOP";

    Student *sPtr = &s;
    std::cout << (*sPtr).mark << "," << (*sPtr).name << std::endl; //   ->
    std::cout << sPtr->mark << "," << sPtr->name << std::endl;
}

void myFunc2()
{
    Student *sPtr = new Student();
    sPtr->mark = 100;
    sPtr->name = "anoop";

    std::cout << (*sPtr).mark << "," << (*sPtr).name << std::endl;
    std::cout << sPtr->mark << "," << sPtr->name << std::endl;

}

// ----------------------------------------------------

class Rectangle
{
public:
    Rectangle(int len,int wid)
    {
        length = len;
        width = wid;
    }
    int getArea()
    {
        return length * width;
    }
    int length,width;
};

void myFunc3()
{
    Rectangle r1(10,20);
    Rectangle *rPtr = &r1;
    std::cout << "Area : " << rPtr->getArea() << std::endl;

    Rectangle *rPtr2 = new Rectangle(20,30);
    std::cout << "Area 2 : " << rPtr2->getArea() << std::endl;
    delete rPtr2;
    std::cout << "Area 2 : " << rPtr2->getArea() << std::endl;

}

int main(int argc, char const *argv[])
{
    myFunc1();
    myFunc2();
    myFunc3();
    return 0;
}