Many instructions read online, or in a semi-known semi-solution state, is considered read the following example to understand the this
pointer
#include <iostream>
using namespace std;
class Box {
public:
// Constructor definition
Box(double l = 2.0, double b = 2.0, double h = 2.0) {
cout <<"Constructor called." << endl;
length = l;
breadth = b;
height = h;
}
double Volume() {
return length * breadth * height;
}
int compare(Box box) {
return this->Volume() > box.Volume();
}
private:
double length; // Length of a box
double breadth; // Breadth of a box
double height; // Height of a box
};
int main(void) {
Box Box1(3.3, 1.2, 1.5); // Declare box1
Box Box2(8.5, 6.0, 2.0); // Declare box2
if(Box1.compare(Box2)) {
cout << "Box2 is smaller than Box1" <<endl;
} else {
cout << "Box2 is equal to or larger than Box1" <<endl;
}
return 0;
}
Constructor called.
Constructor called.
Box2 is equal to or larger than Box1
[Finished in 1.9s]
Description:
expression Box1.compare(Box2)
, Box1
calls the compare
function, compare
the function of the this
pointer now points to Box1
, and therefore compare
an expression of the function return this->Volume() > box.Volume()
becomesreturn Box1->Volume() > box.Volume()
Examples of the above may be written in the form of pointers, as follows
#include <iostream>
using namespace std;
class Box {
public:
// Constructor definition
Box(double l = 2.0, double b = 2.0, double h = 2.0) {
cout <<"Constructor called." << endl;
length = l;
breadth = b;
height = h;
}
double Volume() {
return length * breadth * height;
}
int compare(Box box) {
return this->Volume() > box.Volume();
}
private:
double length; // Length of a box
double breadth; // Breadth of a box
double height; // Height of a box
};
int main(void) {
Box *b1 = new Box(3.3, 1.2, 1.5); // Declare b1
Box *b2 = new Box(8.5, 6.0, 2.0); // Declare b2
if(b1 ->compare(*b2)) {
cout << "b2 is smaller than b1" <<endl;
} else {
cout << "b2 is equal to or larger than b1" <<endl;
}
return 0;
}