The concept of polymorphism inC++
Polymorphism or polymorphism(Polymorphism)It is just a method of writing code that is intended to build a function that executes different commands depending on the object that we pass to it when it is called.
Usually polymorphism is mainly related to inheritance, where the function is based on the parent class, but when we call it we pass an object from one of the classes it inherits from.
How to apply the principle of polymorphism inC++
In the following example, we defined a class whose name Countryis just the basic class for any class that represents a country, and therefore any class we will create to represent a country must inherit from it. In this class we have also prepared 3 abstract functions.
Then we defined a class whose name is a class, and a class Egyptwhose name Australiainherits from the class Countryand they doOverrideFor all functions that they inherited from him.
Then we created a function named printCountryInfo()its task to call all the functions in the object that we pass to it provided that this object was created from a class that inherits from the classCountry.
Finally, we created an object from the class Egyptand an object from the class Australiaand passed each of them to the functionprintCountryInfo().
Example
#include <iostream>
using namespace std;
// Contains 3 abstract functions Country Here we have created a class called
class Country
{
public:
virtual void name() = 0;
virtual void capital() = 0;
virtual void language() = 0;
};
// For the three existing functions that Override inherited from him, and he did Country inherits from the Australia class, here we created an empty class named
class Australia : public Country
{
public:
void name() override
{
cout << "Country: Australia\n";
}
void capital() override
{
cout << "Capital: Canberra\n";
}
void language() override
{
cout << "Language: English\n";
}
};
// For the three existing functions that Override inherited from him, and he did Country inherits from the Egypt class, here we created an empty class named
class Egypt : public Country
{
public:
void name() override
{
cout << "Country: Egypt\n";
}
void capital() override
{
cout << "Capital: Cairo\n";
}
void language() override
{
cout << "Language: Arabic\n";
}
};
// it executes the three functions in it, Country. When called, we pass it the address of an object that inherits from the printCountryInfo class.
void printCountryInfo(Country& country)
{
country.name();
country.capital();
country.language();
cout << "----------------\n";
}
// main() Here we have defined the function
int main()
{
// eg its name is Egypt and a class object au its name is Australiaypt here we created an object of class
Australia au;
Egypt eg;
// In order to call the three functions, au and au, we pass the two objects printCountryInfo() here we call the function
printCountryInfo(au);
printCountryInfo(eg);
return 0;
}
• We will get the following result when running.
Country: Australia Capital: Canberra Language: English ---------------- Country: Egypt Capital: Cairo Language: Arabic ----------------
How to apply the principle of polymorphism with matrices inC++
Ordinary arrays cannot store objects of different classes in them and ensure that this command does not cause any problems because it is not configured for this command, so we will use an advanced type of array to handle in order to teach you how to apply the principle of polymorphism with arrays.
One of the first types of advanced matrices is the type vector, which is the type that we will use shortly, noting that we will explain it in boring detail later in the course.
The object that you create from the class vectorcan store an unlimited number of normal values or objects inside it, and whenever you want, you can add more or delete the ones in it, unlike ordinary arrays that you have to specify its size at the moment of its creation.
In order to create objects from classes vectoryou must include the class vectorfirst.
To put any value inside vectorwe use the function push_back()and to delete any value we use the functionerase() .
In the following example, we have repeated the previous example, but this time in the function, main()we have created an object from the class vectornamed countriesand stored the objects that we created from the class Australiaand Egyptin it.
Example
#include <iostream>
#include <vector>
using namespace std;
// Contains 3 abstract functions Country Here we have created a class called
class Country
{
public:
virtual void name() = 0;
virtual void capital() = 0;
virtual void language() = 0;
};
// For the three existing functions that Override inherited from him, and he did Country inherits from the Australia class, here we created an empty class named
class Australia : public Country
{
public:
void name() override
{
cout << "Country: Australia\n";
}
void capital() override
{
cout << "Capital: Canberra\n";
}
void language() override
{
cout << "Language: English\n";
}
};
// For the three existing functions that Override inherited from him, and he did Country inherits from the Egypt class, here we created an empty class named
class Egypt : public Country
{
public:
void name() override
{
cout << "Country: Egypt\n";
}
void capital() override
{
cout << "Capital: Cairo\n";
}
void language() override
{
cout << "Language: Arabic\n";
}
};
// it executes the three functions in it, Country. When called, we pass it the address of an object that inherits from the printCountryInfo class.
void printCountryInfo(Country& country)
{
country.name();
country.capital();
country.language();
cout << "----------------\n";
}
// main() Here we have defined the function
int main()
{
// eg its name is Egypt and a class object au its name is Australiaypt here we created an object of class
Australia au;
Egypt eg;
// Country we will put in it pointers to objects that inherit from countries called vector Here we have created an object from the class
vector<Country*> countries;
// countries in the object eg and au here we have added the addresses of the two objects
countries.push_back(&au);
countries.push_back(&eg);
// and pass the address of the object to it printCountryInfo() and then it calls the countries function here we created a loop every time it passes an element in the object
for (unsigned i=0; i<countries.size(); i++)
{
printCountryInfo(*countries[i]);
}
return 0;
}
• We will get the following result when running.
Country: Australia Capital: Canberra Language: English ---------------- Country: Egypt Capital: Cairo Language: Arabic ----------------